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	$64.42	11.630%	$71.912	$71.91	$71.90	$71.90
Purchase #2	$46.32	4.792%	$48.5397	$48.54	$48.55	$48.50
Purchase #3	$147.61	11.603%	$164.7372	$164.74	$164.75	$164.70
Purchase #4	$105.35	4.571%	$110.1655	$110.17	$110.15	$110.20
Purchase #5	$160.53	3.798%	$166.6269	$166.63	$166.65	$166.60
Purchase #6	$196.28	13.742%	$223.2528	$223.25	$223.25	$223.30
Purchase #7	$165.48	10.118%	$182.2233	$182.22	$182.20	$182.20
7 purchase totals =	$885.99		$967.4574	$967.46	$967.45	$967.40