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	$124.42	13.546%	$141.2739	$141.27	$141.25	$141.30
Purchase #2	$237.66	10.376%	$262.3196	$262.32	$262.30	$262.30
Purchase #3	$240.33	11.204%	$267.2566	$267.26	$267.25	$267.30
Purchase #4	$144.60	10.187%	$159.3304	$159.33	$159.35	$159.30
Purchase #5	$39.56	7.697%	$42.6049	$42.60	$42.60	$42.60
Purchase #6	$108.33	6.707%	$115.5957	$115.60	$115.60	$115.60
Purchase #7	$165.82	6.338%	$176.3297	$176.33	$176.35	$176.30
7 purchase totals =	$1,060.72		$1,164.7108	$1,164.71	$1,164.70	$1,164.70