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	$149.71	6.574%	$159.5519	$159.55	$159.55	$159.60
Purchase #2	$113.42	4.237%	$118.2256	$118.23	$118.25	$118.20
Purchase #3	$85.65	4.300%	$89.333	$89.33	$89.35	$89.30
Purchase #4	$123.93	9.362%	$135.5323	$135.53	$135.55	$135.50
Purchase #5	$93.31	4.576%	$97.5799	$97.58	$97.60	$97.60
Purchase #6	$218.64	10.187%	$240.9129	$240.91	$240.90	$240.90
Purchase #7	$173.46	10.625%	$191.8901	$191.89	$191.90	$191.90
7 purchase totals =	$958.12		$1,033.0257	$1,033.02	$1,033.10	$1,033.00