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	$77.30	11.603%	$86.2691	$86.27	$86.25	$86.30
Purchase #2	$82.26	12.737%	$92.7375	$92.74	$92.75	$92.70
Purchase #3	$37.56	12.217%	$42.1487	$42.15	$42.15	$42.10
Purchase #4	$10.70	3.601%	$11.0853	$11.09	$11.10	$11.10
Purchase #5	$230.91	4.545%	$241.4049	$241.40	$241.40	$241.40
Purchase #6	$89.67	6.306%	$95.3246	$95.32	$95.30	$95.30
Purchase #7	$179.86	4.734%	$188.3746	$188.37	$188.35	$188.40
7 purchase totals =	$708.26		$757.3447	$757.34	$757.30	$757.30