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	$231.65	11.834%	$259.0635	$259.06	$259.05	$259.10
Purchase #2	$168.71	9.759%	$185.1744	$185.17	$185.15	$185.20
Purchase #3	$114.52	13.503%	$129.9836	$129.98	$130.00	$130.00
Purchase #4	$45.77	9.401%	$50.0728	$50.07	$50.05	$50.10
Purchase #5	$64.73	11.650%	$72.271	$72.27	$72.25	$72.30
Purchase #6	$131.73	13.543%	$149.5702	$149.57	$149.55	$149.60
Purchase #7	$159.30	4.482%	$166.4398	$166.44	$166.45	$166.40
7 purchase totals =	$916.41		$1,012.5753	$1,012.56	$1,012.50	$1,012.70