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	$61.87	12.312%	$69.4874	$69.49	$69.50	$69.50
Purchase #2	$93.69	12.157%	$105.0799	$105.08	$105.10	$105.10
Purchase #3	$106.92	4.369%	$111.5913	$111.59	$111.60	$111.60
Purchase #4	$134.94	13.248%	$152.8169	$152.82	$152.80	$152.80
Purchase #5	$5.91	7.410%	$6.3479	$6.35	$6.35	$6.30
Purchase #6	$239.61	6.741%	$255.7621	$255.76	$255.75	$255.80
Purchase #7	$62.66	7.148%	$67.1389	$67.14	$67.15	$67.10
7 purchase totals =	$705.60		$768.2244	$768.23	$768.25	$768.20