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	$40.33	12.171%	$45.2386	$45.24	$45.25	$45.20
Purchase #2	$106.59	5.189%	$112.121	$112.12	$112.10	$112.10
Purchase #3	$249.94	4.176%	$260.3775	$260.38	$260.40	$260.40
Purchase #4	$193.87	3.598%	$200.8454	$200.85	$200.85	$200.80
Purchase #5	$84.37	5.628%	$89.1183	$89.12	$89.10	$89.10
Purchase #6	$159.99	3.590%	$165.7336	$165.73	$165.75	$165.70
Purchase #7	$233.48	7.390%	$250.7342	$250.73	$250.75	$250.70
7 purchase totals =	$1,068.57		$1,124.1686	$1,124.17	$1,124.20	$1,124.00