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	$38.47	5.616%	$40.6305	$40.63	$40.65	$40.60
Purchase #2	$169.70	12.654%	$191.1738	$191.17	$191.15	$191.20
Purchase #3	$151.89	8.787%	$165.2366	$165.24	$165.25	$165.20
Purchase #4	$176.43	10.476%	$194.9128	$194.91	$194.90	$194.90
Purchase #5	$212.26	5.407%	$223.7369	$223.74	$223.75	$223.70
Purchase #6	$173.91	7.716%	$187.3289	$187.33	$187.35	$187.30
Purchase #7	$89.94	9.486%	$98.4717	$98.47	$98.45	$98.50
7 purchase totals =	$1,012.60		$1,101.4912	$1,101.49	$1,101.50	$1,101.40