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	$158.89	7.829%	$171.3295	$171.33	$171.35	$171.30
Purchase #2	$66.97	8.218%	$72.4736	$72.47	$72.45	$72.50
Purchase #3	$39.34	7.433%	$42.2641	$42.26	$42.25	$42.30
Purchase #4	$39.54	3.368%	$40.8717	$40.87	$40.85	$40.90
Purchase #5	$179.89	3.777%	$186.6844	$186.68	$186.70	$186.70
Purchase #6	$176.87	9.469%	$193.6178	$193.62	$193.60	$193.60
Purchase #7	$211.47	11.412%	$235.603	$235.60	$235.60	$235.60
7 purchase totals =	$872.97		$942.8441	$942.83	$942.80	$942.90