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	$185.86	5.871%	$196.7718	$196.77	$196.75	$196.80
Purchase #2	$15.35	3.610%	$15.9041	$15.90	$15.90	$15.90
Purchase #3	$139.55	4.667%	$146.0628	$146.06	$146.05	$146.10
Purchase #4	$250.83	4.646%	$262.4836	$262.48	$262.50	$262.50
Purchase #5	$76.59	4.274%	$79.8635	$79.86	$79.85	$79.90
Purchase #6	$198.70	10.427%	$219.4184	$219.42	$219.40	$219.40
Purchase #7	$64.82	11.290%	$72.1382	$72.14	$72.15	$72.10
7 purchase totals =	$931.70		$992.6424	$992.63	$992.60	$992.70