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	$55.47	7.869%	$59.8349	$59.83	$59.85	$59.80
Purchase #2	$28.69	13.576%	$32.585	$32.59	$32.60	$32.60
Purchase #3	$91.28	5.576%	$96.3698	$96.37	$96.35	$96.40
Purchase #4	$92.91	9.481%	$101.7188	$101.72	$101.70	$101.70
Purchase #5	$201.87	5.595%	$213.1646	$213.16	$213.15	$213.20
Purchase #6	$226.94	6.328%	$241.3008	$241.30	$241.30	$241.30
Purchase #7	$165.40	9.258%	$180.7127	$180.71	$180.70	$180.70
7 purchase totals =	$862.56		$925.6866	$925.68	$925.65	$925.70