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	$243.89	7.634%	$262.5086	$262.51	$262.50	$262.50
Purchase #2	$110.75	6.111%	$117.5179	$117.52	$117.50	$117.50
Purchase #3	$171.27	4.546%	$179.0559	$179.06	$179.05	$179.10
Purchase #4	$72.25	9.372%	$79.0213	$79.02	$79.00	$79.00
Purchase #5	$82.89	8.681%	$90.0857	$90.09	$90.10	$90.10
Purchase #6	$223.29	9.131%	$243.6786	$243.68	$243.70	$243.70
Purchase #7	$97.95	11.862%	$109.5688	$109.57	$109.55	$109.60
7 purchase totals =	$1,002.29		$1,081.4368	$1,081.45	$1,081.40	$1,081.50