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	$169.38	11.351%	$188.6063	$188.61	$188.60	$188.60
Purchase #2	$177.27	7.368%	$190.3313	$190.33	$190.35	$190.30
Purchase #3	$173.27	12.741%	$195.3463	$195.35	$195.35	$195.30
Purchase #4	$106.76	10.254%	$117.7072	$117.71	$117.70	$117.70
Purchase #5	$32.73	6.300%	$34.792	$34.79	$34.80	$34.80
Purchase #6	$211.59	5.319%	$222.8445	$222.84	$222.85	$222.80
Purchase #7	$117.98	8.165%	$127.6131	$127.61	$127.60	$127.60
7 purchase totals =	$988.98		$1,077.2407	$1,077.24	$1,077.25	$1,077.10