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	$54.73	13.116%	$61.9084	$61.91	$61.90	$61.90
Purchase #2	$59.76	5.596%	$63.1042	$63.10	$63.10	$63.10
Purchase #3	$52.78	5.135%	$55.4903	$55.49	$55.50	$55.50
Purchase #4	$174.72	9.272%	$190.92	$190.92	$190.90	$190.90
Purchase #5	$28.26	10.536%	$31.2375	$31.24	$31.25	$31.20
Purchase #6	$78.75	8.733%	$85.6272	$85.63	$85.65	$85.60
Purchase #7	$225.84	9.588%	$247.4935	$247.49	$247.50	$247.50
7 purchase totals =	$674.84		$735.7811	$735.78	$735.80	$735.70