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	$87.96	3.446%	$90.9911	$90.99	$91.00	$91.00
Purchase #2	$191.91	10.551%	$212.1584	$212.16	$212.15	$212.20
Purchase #3	$68.87	3.288%	$71.1344	$71.13	$71.15	$71.10
Purchase #4	$65.45	8.731%	$71.1644	$71.16	$71.15	$71.20
Purchase #5	$179.67	4.758%	$188.2187	$188.22	$188.20	$188.20
Purchase #6	$201.98	11.848%	$225.9106	$225.91	$225.90	$225.90
Purchase #7	$100.99	10.656%	$111.7515	$111.75	$111.75	$111.80
7 purchase totals =	$896.83		$971.3291	$971.32	$971.30	$971.40