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	$40.59	9.547%	$44.4651	$44.47	$44.45	$44.50
Purchase #2	$35.61	6.343%	$37.8687	$37.87	$37.85	$37.90
Purchase #3	$71.25	10.671%	$78.8531	$78.85	$78.85	$78.90
Purchase #4	$66.26	7.529%	$71.2487	$71.25	$71.25	$71.20
Purchase #5	$28.56	8.403%	$30.9599	$30.96	$30.95	$31.00
Purchase #6	$165.71	12.167%	$185.8719	$185.87	$185.85	$185.90
Purchase #7	$7.36	7.496%	$7.9117	$7.91	$7.90	$7.90
7 purchase totals =	$415.34		$457.1791	$457.18	$457.10	$457.30