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	$167.32	13.267%	$189.5183	$189.52	$189.50	$189.50
Purchase #2	$12.92	3.621%	$13.3878	$13.39	$13.40	$13.40
Purchase #3	$54.59	12.646%	$61.4935	$61.49	$61.50	$61.50
Purchase #4	$154.68	13.248%	$175.172	$175.17	$175.15	$175.20
Purchase #5	$59.33	13.795%	$67.5146	$67.51	$67.50	$67.50
Purchase #6	$57.84	11.756%	$64.6397	$64.64	$64.65	$64.60
Purchase #7	$94.73	9.441%	$103.6735	$103.67	$103.65	$103.70
7 purchase totals =	$601.41		$675.3994	$675.39	$675.35	$675.40