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	$86.78	13.213%	$98.2462	$98.25	$98.25	$98.20
Purchase #2	$159.60	3.456%	$165.1158	$165.12	$165.10	$165.10
Purchase #3	$147.69	4.637%	$154.5384	$154.54	$154.55	$154.50
Purchase #4	$128.67	6.815%	$137.4389	$137.44	$137.45	$137.40
Purchase #5	$159.45	10.151%	$175.6358	$175.64	$175.65	$175.60
Purchase #6	$132.69	6.149%	$140.8491	$140.85	$140.85	$140.80
Purchase #7	$248.27	6.556%	$264.5466	$264.55	$264.55	$264.50
7 purchase totals =	$1,063.15		$1,136.3708	$1,136.39	$1,136.40	$1,136.10