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	$61.85	9.557%	$67.761	$67.76	$67.75	$67.80
Purchase #2	$120.77	5.627%	$127.5657	$127.57	$127.55	$127.60
Purchase #3	$153.93	3.757%	$159.7132	$159.71	$159.70	$159.70
Purchase #4	$157.92	4.528%	$165.0706	$165.07	$165.05	$165.10
Purchase #5	$36.55	7.818%	$39.4075	$39.41	$39.40	$39.40
Purchase #6	$79.91	7.467%	$85.8769	$85.88	$85.90	$85.90
Purchase #7	$192.67	10.108%	$212.1451	$212.15	$212.15	$212.10
7 purchase totals =	$803.60		$857.5400	$857.55	$857.50	$857.60