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	$155.56	6.140%	$165.1114	$165.11	$165.10	$165.10
Purchase #2	$40.34	5.505%	$42.5607	$42.56	$42.55	$42.60
Purchase #3	$89.43	12.629%	$100.7241	$100.72	$100.70	$100.70
Purchase #4	$60.41	6.819%	$64.5294	$64.53	$64.55	$64.50
Purchase #5	$218.44	6.871%	$233.449	$233.45	$233.45	$233.40
Purchase #6	$175.54	4.553%	$183.5323	$183.53	$183.55	$183.50
Purchase #7	$52.25	4.857%	$54.7878	$54.79	$54.80	$54.80
7 purchase totals =	$791.97		$844.6947	$844.69	$844.70	$844.60