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	$127.48	3.503%	$131.9456	$131.95	$131.95	$131.90
Purchase #2	$55.61	12.530%	$62.5779	$62.58	$62.60	$62.60
Purchase #3	$224.44	10.266%	$247.481	$247.48	$247.50	$247.50
Purchase #4	$83.77	10.830%	$92.8423	$92.84	$92.85	$92.80
Purchase #5	$27.45	5.549%	$28.9732	$28.97	$28.95	$29.00
Purchase #6	$226.80	9.560%	$248.4821	$248.48	$248.50	$248.50
Purchase #7	$112.80	12.710%	$127.1369	$127.14	$127.15	$127.10
7 purchase totals =	$858.35		$939.4390	$939.44	$939.50	$939.40