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	$108.38	3.134%	$111.7766	$111.78	$111.80	$111.80
Purchase #2	$167.34	8.267%	$181.174	$181.17	$181.15	$181.20
Purchase #3	$107.59	3.475%	$111.3288	$111.33	$111.35	$111.30
Purchase #4	$124.82	13.640%	$141.8454	$141.85	$141.85	$141.80
Purchase #5	$168.88	6.321%	$179.5549	$179.55	$179.55	$179.60
Purchase #6	$237.68	12.557%	$267.5255	$267.53	$267.55	$267.50
Purchase #7	$137.72	8.429%	$149.3284	$149.33	$149.35	$149.30
7 purchase totals =	$1,052.41		$1,142.5336	$1,142.54	$1,142.60	$1,142.50