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	$154.40	7.305%	$165.6789	$165.68	$165.70	$165.70
Purchase #2	$142.81	12.258%	$160.3156	$160.32	$160.30	$160.30
Purchase #3	$189.97	5.297%	$200.0327	$200.03	$200.05	$200.00
Purchase #4	$217.77	12.715%	$245.4595	$245.46	$245.45	$245.50
Purchase #5	$178.78	4.223%	$186.3299	$186.33	$186.35	$186.30
Purchase #6	$31.85	4.713%	$33.3511	$33.35	$33.35	$33.40
Purchase #7	$32.70	13.472%	$37.1053	$37.11	$37.10	$37.10
7 purchase totals =	$948.28		$1,028.2730	$1,028.28	$1,028.30	$1,028.30