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	$246.61	11.642%	$275.3203	$275.32	$275.30	$275.30
Purchase #2	$94.96	9.361%	$103.8492	$103.85	$103.85	$103.80
Purchase #3	$92.54	11.608%	$103.282	$103.28	$103.30	$103.30
Purchase #4	$204.81	3.214%	$211.3926	$211.39	$211.40	$211.40
Purchase #5	$91.59	10.855%	$101.5321	$101.53	$101.55	$101.50
Purchase #6	$235.76	9.501%	$258.1596	$258.16	$258.15	$258.20
Purchase #7	$53.71	12.453%	$60.3985	$60.40	$60.40	$60.40
7 purchase totals =	$1,019.98		$1,113.9343	$1,113.93	$1,113.95	$1,113.90