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	$190.34	9.359%	$208.1539	$208.15	$208.15	$208.20
Purchase #2	$152.67	8.669%	$165.905	$165.91	$165.90	$165.90
Purchase #3	$173.98	13.108%	$196.7853	$196.79	$196.80	$196.80
Purchase #4	$177.57	12.514%	$199.7911	$199.79	$199.80	$199.80
Purchase #5	$99.74	3.285%	$103.0165	$103.02	$103.00	$103.00
Purchase #6	$216.87	8.755%	$235.857	$235.86	$235.85	$235.90
Purchase #7	$40.32	3.164%	$41.5957	$41.60	$41.60	$41.60
7 purchase totals =	$1,051.49		$1,151.1045	$1,151.12	$1,151.10	$1,151.20