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	$44.93	3.536%	$46.5187	$46.52	$46.50	$46.50
Purchase #2	$168.37	5.821%	$178.1708	$178.17	$178.15	$178.20
Purchase #3	$23.49	12.362%	$26.3938	$26.39	$26.40	$26.40
Purchase #4	$119.81	6.575%	$127.6875	$127.69	$127.70	$127.70
Purchase #5	$35.66	4.356%	$37.2133	$37.21	$37.20	$37.20
Purchase #6	$95.76	4.550%	$100.1171	$100.12	$100.10	$100.10
Purchase #7	$145.73	6.478%	$155.1704	$155.17	$155.15	$155.20
7 purchase totals =	$633.75		$671.2716	$671.27	$671.20	$671.30