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	$158.86	10.367%	$175.329	$175.33	$175.35	$175.30
Purchase #2	$38.80	8.458%	$42.0817	$42.08	$42.10	$42.10
Purchase #3	$151.30	11.109%	$168.1079	$168.11	$168.10	$168.10
Purchase #4	$160.56	13.197%	$181.7491	$181.75	$181.75	$181.70
Purchase #5	$102.61	10.364%	$113.2445	$113.24	$113.25	$113.20
Purchase #6	$84.70	8.355%	$91.7767	$91.78	$91.80	$91.80
Purchase #7	$225.79	5.813%	$238.9152	$238.92	$238.90	$238.90
7 purchase totals =	$922.62		$1,011.2041	$1,011.21	$1,011.25	$1,011.10