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	$246.98	11.478%	$275.3284	$275.33	$275.35	$275.30
Purchase #2	$90.91	9.833%	$99.8492	$99.85	$99.85	$99.80
Purchase #3	$10.41	4.272%	$10.8547	$10.85	$10.85	$10.90
Purchase #4	$187.62	12.554%	$211.1738	$211.17	$211.15	$211.20
Purchase #5	$109.59	6.846%	$117.0925	$117.09	$117.10	$117.10
Purchase #6	$219.93	10.401%	$242.8049	$242.80	$242.80	$242.80
Purchase #7	$56.32	6.449%	$59.9521	$59.95	$59.95	$60.00
7 purchase totals =	$921.76		$1,017.0556	$1,017.04	$1,017.05	$1,017.10