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	$133.65	4.134%	$139.1751	$139.18	$139.20	$139.20
Purchase #2	$157.61	5.495%	$166.2707	$166.27	$166.25	$166.30
Purchase #3	$216.27	5.362%	$227.8664	$227.87	$227.85	$227.90
Purchase #4	$27.92	7.131%	$29.911	$29.91	$29.90	$29.90
Purchase #5	$54.50	4.397%	$56.8964	$56.90	$56.90	$56.90
Purchase #6	$114.36	10.514%	$126.3838	$126.38	$126.40	$126.40
Purchase #7	$245.96	4.110%	$256.069	$256.07	$256.05	$256.10
7 purchase totals =	$950.27		$1,002.5724	$1,002.58	$1,002.55	$1,002.70