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	$106.81	6.834%	$114.1094	$114.11	$114.10	$114.10
Purchase #2	$83.98	6.762%	$89.6587	$89.66	$89.65	$89.70
Purchase #3	$36.74	7.755%	$39.5892	$39.59	$39.60	$39.60
Purchase #4	$176.56	7.179%	$189.2352	$189.24	$189.25	$189.20
Purchase #5	$80.84	12.649%	$91.0655	$91.07	$91.05	$91.10
Purchase #6	$212.69	5.120%	$223.5797	$223.58	$223.60	$223.60
Purchase #7	$140.41	7.870%	$151.4603	$151.46	$151.45	$151.50
7 purchase totals =	$838.03		$898.6980	$898.71	$898.70	$898.80