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	$185.98	10.426%	$205.3703	$205.37	$205.35	$205.40
Purchase #2	$79.41	12.741%	$89.5276	$89.53	$89.55	$89.50
Purchase #3	$237.90	8.645%	$258.4665	$258.47	$258.45	$258.50
Purchase #4	$138.54	6.811%	$147.976	$147.98	$148.00	$148.00
Purchase #5	$247.27	11.301%	$275.214	$275.21	$275.20	$275.20
Purchase #6	$93.69	8.147%	$101.3229	$101.32	$101.30	$101.30
Purchase #7	$21.75	3.393%	$22.488	$22.49	$22.50	$22.50
7 purchase totals =	$1,004.54		$1,100.3653	$1,100.37	$1,100.35	$1,100.40