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	$190.93	10.583%	$211.1361	$211.14	$211.15	$211.10
Purchase #2	$185.48	10.249%	$204.4898	$204.49	$204.50	$204.50
Purchase #3	$67.51	6.525%	$71.915	$71.92	$71.90	$71.90
Purchase #4	$137.70	12.381%	$154.7486	$154.75	$154.75	$154.70
Purchase #5	$160.59	9.779%	$176.2941	$176.29	$176.30	$176.30
Purchase #6	$200.74	4.831%	$210.4377	$210.44	$210.45	$210.40
Purchase #7	$33.55	11.172%	$37.2982	$37.30	$37.30	$37.30
7 purchase totals =	$976.50		$1,066.3195	$1,066.33	$1,066.35	$1,066.20