Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$134.59	9.550%	$147.4433	$147.44	$147.45	$147.40
Purchase #2	$151.50	10.151%	$166.8788	$166.88	$166.90	$166.90
Purchase #3	$165.79	11.767%	$185.2985	$185.30	$185.30	$185.30
Purchase #4	$223.44	13.257%	$253.0614	$253.06	$253.05	$253.10
Purchase #5	$162.33	10.149%	$178.8049	$178.80	$178.80	$178.80
Purchase #6	$90.47	13.713%	$102.8762	$102.88	$102.90	$102.90
Purchase #7	$114.90	3.285%	$118.6745	$118.67	$118.65	$118.70
7 purchase totals =	$1,043.02		$1,153.0376	$1,153.03	$1,153.05	$1,153.10