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	$86.67	5.124%	$91.111	$91.11	$91.10	$91.10
Purchase #2	$250.84	7.265%	$269.0635	$269.06	$269.05	$269.10
Purchase #3	$120.70	11.562%	$134.6553	$134.66	$134.65	$134.70
Purchase #4	$245.91	13.794%	$279.8308	$279.83	$279.85	$279.80
Purchase #5	$30.94	9.451%	$33.8641	$33.86	$33.85	$33.90
Purchase #6	$173.45	7.213%	$185.9609	$185.96	$185.95	$186.00
Purchase #7	$141.98	7.344%	$152.407	$152.41	$152.40	$152.40
7 purchase totals =	$1,050.49		$1,146.8926	$1,146.89	$1,146.85	$1,147.00