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	$171.72	9.702%	$188.3803	$188.38	$188.40	$188.40
Purchase #2	$67.39	3.656%	$69.8538	$69.85	$69.85	$69.90
Purchase #3	$145.64	10.388%	$160.7691	$160.77	$160.75	$160.80
Purchase #4	$126.36	3.807%	$131.1705	$131.17	$131.15	$131.20
Purchase #5	$23.98	5.833%	$25.3788	$25.38	$25.40	$25.40
Purchase #6	$119.51	6.485%	$127.2602	$127.26	$127.25	$127.30
Purchase #7	$155.75	6.552%	$165.9547	$165.95	$165.95	$166.00
7 purchase totals =	$810.35		$868.7674	$868.76	$868.75	$869.00