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	$159.84	4.516%	$167.0584	$167.06	$167.05	$167.10
Purchase #2	$67.68	6.439%	$72.0379	$72.04	$72.05	$72.00
Purchase #3	$56.43	5.402%	$59.4783	$59.48	$59.50	$59.50
Purchase #4	$224.69	10.746%	$248.8352	$248.84	$248.85	$248.80
Purchase #5	$89.79	6.702%	$95.8077	$95.81	$95.80	$95.80
Purchase #6	$66.89	13.154%	$75.6887	$75.69	$75.70	$75.70
Purchase #7	$209.90	4.632%	$219.6226	$219.62	$219.60	$219.60
7 purchase totals =	$875.22		$938.5288	$938.54	$938.55	$938.50