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	$89.72	12.532%	$100.9637	$100.96	$100.95	$101.00
Purchase #2	$112.25	3.240%	$115.8869	$115.89	$115.90	$115.90
Purchase #3	$73.51	4.156%	$76.5651	$76.57	$76.55	$76.60
Purchase #4	$22.85	5.129%	$24.022	$24.02	$24.00	$24.00
Purchase #5	$93.37	7.532%	$100.4026	$100.40	$100.40	$100.40
Purchase #6	$64.70	12.168%	$72.5727	$72.57	$72.55	$72.60
Purchase #7	$216.75	3.361%	$224.035	$224.04	$224.05	$224.00
7 purchase totals =	$673.15		$714.4480	$714.45	$714.40	$714.50