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	$87.92	9.470%	$96.246	$96.25	$96.25	$96.20
Purchase #2	$245.51	12.375%	$275.8919	$275.89	$275.90	$275.90
Purchase #3	$124.55	10.561%	$137.7037	$137.70	$137.70	$137.70
Purchase #4	$84.55	6.327%	$89.8995	$89.90	$89.90	$89.90
Purchase #5	$55.79	11.173%	$62.0234	$62.02	$62.00	$62.00
Purchase #6	$26.28	13.748%	$29.893	$29.89	$29.90	$29.90
Purchase #7	$97.97	3.193%	$101.0982	$101.10	$101.10	$101.10
7 purchase totals =	$722.57		$792.7557	$792.75	$792.75	$792.70