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	$238.28	6.390%	$253.5061	$253.51	$253.50	$253.50
Purchase #2	$169.48	5.237%	$178.3557	$178.36	$178.35	$178.40
Purchase #3	$178.75	9.503%	$195.7366	$195.74	$195.75	$195.70
Purchase #4	$41.79	8.151%	$45.1963	$45.20	$45.20	$45.20
Purchase #5	$74.98	6.123%	$79.571	$79.57	$79.55	$79.60
Purchase #6	$83.86	7.748%	$90.3575	$90.36	$90.35	$90.40
Purchase #7	$98.50	7.427%	$105.8156	$105.82	$105.80	$105.80
7 purchase totals =	$885.64		$948.5388	$948.56	$948.50	$948.60