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	$41.42	11.844%	$46.3258	$46.33	$46.35	$46.30
Purchase #2	$58.88	13.500%	$66.8288	$66.83	$66.85	$66.80
Purchase #3	$82.49	8.560%	$89.5511	$89.55	$89.55	$89.60
Purchase #4	$224.86	10.386%	$248.214	$248.21	$248.20	$248.20
Purchase #5	$230.35	3.228%	$237.7857	$237.79	$237.80	$237.80
Purchase #6	$245.52	10.299%	$270.8061	$270.81	$270.80	$270.80
Purchase #7	$130.64	10.124%	$143.866	$143.87	$143.85	$143.90
7 purchase totals =	$1,014.16		$1,103.3775	$1,103.39	$1,103.40	$1,103.40