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	$233.53	9.204%	$255.0241	$255.02	$255.00	$255.00
Purchase #2	$18.98	9.414%	$20.7668	$20.77	$20.75	$20.80
Purchase #3	$55.61	4.144%	$57.9145	$57.91	$57.90	$57.90
Purchase #4	$238.93	10.258%	$263.4394	$263.44	$263.45	$263.40
Purchase #5	$125.48	9.219%	$137.048	$137.05	$137.05	$137.00
Purchase #6	$185.89	9.698%	$203.9176	$203.92	$203.90	$203.90
Purchase #7	$127.30	11.278%	$141.6569	$141.66	$141.65	$141.70
7 purchase totals =	$985.72		$1,079.7673	$1,079.77	$1,079.70	$1,079.70