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	$64.91	3.448%	$67.1481	$67.15	$67.15	$67.10
Purchase #2	$72.25	11.372%	$80.4663	$80.47	$80.45	$80.50
Purchase #3	$61.77	13.220%	$69.936	$69.94	$69.95	$69.90
Purchase #4	$9.34	8.721%	$10.1545	$10.15	$10.15	$10.20
Purchase #5	$79.63	3.593%	$82.4911	$82.49	$82.50	$82.50
Purchase #6	$127.98	3.154%	$132.0165	$132.02	$132.00	$132.00
Purchase #7	$64.82	9.538%	$71.0025	$71.00	$71.00	$71.00
7 purchase totals =	$480.70		$513.2150	$513.22	$513.20	$513.20