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	$125.78	13.761%	$143.0886	$143.09	$143.10	$143.10
Purchase #2	$236.77	9.291%	$258.7683	$258.77	$258.75	$258.80
Purchase #3	$83.84	9.160%	$91.5197	$91.52	$91.50	$91.50
Purchase #4	$151.57	4.444%	$158.3058	$158.31	$158.30	$158.30
Purchase #5	$79.50	7.488%	$85.453	$85.45	$85.45	$85.50
Purchase #6	$192.44	13.300%	$218.0345	$218.03	$218.05	$218.00
Purchase #7	$118.39	6.374%	$125.9362	$125.94	$125.95	$125.90
7 purchase totals =	$988.29		$1,081.1061	$1,081.11	$1,081.10	$1,081.10