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	$67.27	4.851%	$70.5333	$70.53	$70.55	$70.50
Purchase #2	$178.33	11.181%	$198.2691	$198.27	$198.25	$198.30
Purchase #3	$104.74	5.133%	$110.1163	$110.12	$110.10	$110.10
Purchase #4	$174.68	6.429%	$185.9102	$185.91	$185.90	$185.90
Purchase #5	$62.61	12.717%	$70.5721	$70.57	$70.55	$70.60
Purchase #6	$29.37	10.120%	$32.3422	$32.34	$32.35	$32.30
Purchase #7	$240.52	4.584%	$251.5454	$251.55	$251.55	$251.50
7 purchase totals =	$857.52		$919.2886	$919.29	$919.25	$919.20