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	$57.90	13.654%	$65.8057	$65.81	$65.80	$65.80
Purchase #2	$36.83	11.863%	$41.1991	$41.20	$41.20	$41.20
Purchase #3	$49.42	12.307%	$55.5021	$55.50	$55.50	$55.50
Purchase #4	$84.77	8.776%	$92.2094	$92.21	$92.20	$92.20
Purchase #5	$58.79	3.277%	$60.7165	$60.72	$60.70	$60.70
Purchase #6	$38.69	9.659%	$42.4271	$42.43	$42.45	$42.40
Purchase #7	$89.27	3.714%	$92.5855	$92.59	$92.60	$92.60
7 purchase totals =	$415.67		$450.4454	$450.46	$450.45	$450.40