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	$41.79	10.146%	$46.03	$46.03	$46.05	$46.00
Purchase #2	$112.54	11.852%	$125.8782	$125.88	$125.90	$125.90
Purchase #3	$26.36	9.710%	$28.9196	$28.92	$28.90	$28.90
Purchase #4	$92.56	13.854%	$105.3833	$105.38	$105.40	$105.40
Purchase #5	$229.62	13.400%	$260.3891	$260.39	$260.40	$260.40
Purchase #6	$80.65	13.479%	$91.5208	$91.52	$91.50	$91.50
Purchase #7	$51.52	5.512%	$54.3598	$54.36	$54.35	$54.40
7 purchase totals =	$635.04		$712.4808	$712.48	$712.50	$712.50