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	$61.72	13.764%	$70.2151	$70.22	$70.20	$70.20
Purchase #2	$241.35	3.788%	$250.4923	$250.49	$250.50	$250.50
Purchase #3	$96.76	12.201%	$108.5657	$108.57	$108.55	$108.60
Purchase #4	$225.42	3.686%	$233.729	$233.73	$233.75	$233.70
Purchase #5	$40.53	9.689%	$44.457	$44.46	$44.45	$44.50
Purchase #6	$37.31	8.592%	$40.5157	$40.52	$40.50	$40.50
Purchase #7	$165.94	5.241%	$174.6369	$174.64	$174.65	$174.60
7 purchase totals =	$869.03		$922.6117	$922.63	$922.60	$922.60