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	$54.46	9.530%	$59.65	$59.65	$59.65	$59.70
Purchase #2	$219.42	7.133%	$235.0712	$235.07	$235.05	$235.10
Purchase #3	$216.47	5.707%	$228.8239	$228.82	$228.80	$228.80
Purchase #4	$40.58	8.130%	$43.8792	$43.88	$43.90	$43.90
Purchase #5	$249.27	6.136%	$264.5652	$264.57	$264.55	$264.60
Purchase #6	$68.63	7.801%	$73.9838	$73.98	$74.00	$74.00
Purchase #7	$99.81	11.420%	$111.2083	$111.21	$111.20	$111.20
7 purchase totals =	$948.64		$1,017.1816	$1,017.18	$1,017.15	$1,017.30