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	$89.51	11.199%	$99.5342	$99.53	$99.55	$99.50
Purchase #2	$24.30	3.437%	$25.1352	$25.14	$25.15	$25.10
Purchase #3	$168.78	11.406%	$188.031	$188.03	$188.05	$188.00
Purchase #4	$176.67	11.275%	$196.5895	$196.59	$196.60	$196.60
Purchase #5	$30.25	13.263%	$34.2621	$34.26	$34.25	$34.30
Purchase #6	$165.62	7.362%	$177.8129	$177.81	$177.80	$177.80
Purchase #7	$23.93	4.586%	$25.0274	$25.03	$25.05	$25.00
7 purchase totals =	$679.06		$746.3923	$746.39	$746.45	$746.30