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	$142.78	7.389%	$153.33	$153.33	$153.35	$153.30
Purchase #2	$140.95	12.586%	$158.69	$158.69	$158.70	$158.70
Purchase #3	$88.42	9.236%	$96.5865	$96.59	$96.60	$96.60
Purchase #4	$165.86	7.487%	$178.2779	$178.28	$178.30	$178.30
Purchase #5	$212.34	7.373%	$227.9958	$228.00	$228.00	$228.00
Purchase #6	$106.51	4.738%	$111.5564	$111.56	$111.55	$111.60
Purchase #7	$58.33	4.774%	$61.1147	$61.11	$61.10	$61.10
7 purchase totals =	$915.19		$987.5513	$987.56	$987.60	$987.60