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	$141.31	5.263%	$148.7471	$148.75	$148.75	$148.70
Purchase #2	$179.31	3.242%	$185.1232	$185.12	$185.10	$185.10
Purchase #3	$52.53	3.337%	$54.2829	$54.28	$54.30	$54.30
Purchase #4	$165.53	13.182%	$187.3502	$187.35	$187.35	$187.40
Purchase #5	$52.38	11.444%	$58.3744	$58.37	$58.35	$58.40
Purchase #6	$14.53	6.810%	$15.5195	$15.52	$15.50	$15.50
Purchase #7	$235.66	6.428%	$250.8082	$250.81	$250.80	$250.80
7 purchase totals =	$841.25		$900.2055	$900.20	$900.15	$900.20