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	$162.83	7.176%	$174.5147	$174.51	$174.50	$174.50
Purchase #2	$94.39	5.411%	$99.4974	$99.50	$99.50	$99.50
Purchase #3	$45.26	12.311%	$50.832	$50.83	$50.85	$50.80
Purchase #4	$120.80	11.448%	$134.6292	$134.63	$134.65	$134.60
Purchase #5	$238.70	13.830%	$271.7122	$271.71	$271.70	$271.70
Purchase #6	$46.55	7.204%	$49.9035	$49.90	$49.90	$49.90
Purchase #7	$32.52	3.605%	$33.6923	$33.69	$33.70	$33.70
7 purchase totals =	$741.05		$814.7813	$814.77	$814.80	$814.70