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	$85.54	11.668%	$95.5208	$95.52	$95.50	$95.50
Purchase #2	$137.97	10.498%	$152.4541	$152.45	$152.45	$152.50
Purchase #3	$207.79	12.872%	$234.5367	$234.54	$234.55	$234.50
Purchase #4	$162.76	8.426%	$176.4742	$176.47	$176.45	$176.50
Purchase #5	$155.90	10.594%	$172.416	$172.42	$172.40	$172.40
Purchase #6	$169.54	9.496%	$185.6395	$185.64	$185.65	$185.60
Purchase #7	$204.73	12.478%	$230.2762	$230.28	$230.30	$230.30
7 purchase totals =	$1,124.23		$1,247.3175	$1,247.32	$1,247.30	$1,247.30