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	$134.30	10.526%	$148.4364	$148.44	$148.45	$148.40
Purchase #2	$234.48	7.713%	$252.5654	$252.57	$252.55	$252.60
Purchase #3	$81.75	9.391%	$89.4271	$89.43	$89.45	$89.40
Purchase #4	$55.90	6.408%	$59.4821	$59.48	$59.50	$59.50
Purchase #5	$135.75	5.452%	$143.1511	$143.15	$143.15	$143.20
Purchase #6	$113.47	13.782%	$129.1084	$129.11	$129.10	$129.10
Purchase #7	$200.84	4.108%	$209.0905	$209.09	$209.10	$209.10
7 purchase totals =	$956.49		$1,031.2610	$1,031.27	$1,031.30	$1,031.30