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	$46.53	5.419%	$49.0515	$49.05	$49.05	$49.10
Purchase #2	$99.72	11.427%	$111.115	$111.12	$111.10	$111.10
Purchase #3	$198.88	13.874%	$226.4726	$226.47	$226.45	$226.50
Purchase #4	$205.51	10.658%	$227.4133	$227.41	$227.40	$227.40
Purchase #5	$65.33	10.771%	$72.3667	$72.37	$72.35	$72.40
Purchase #6	$187.81	8.436%	$203.6537	$203.65	$203.65	$203.70
Purchase #7	$191.73	3.709%	$198.8413	$198.84	$198.85	$198.80
7 purchase totals =	$995.51		$1,088.9141	$1,088.91	$1,088.85	$1,089.00