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	$61.61	9.659%	$67.5609	$67.56	$67.55	$67.60
Purchase #2	$69.58	4.764%	$72.8948	$72.89	$72.90	$72.90
Purchase #3	$187.36	13.566%	$212.7773	$212.78	$212.80	$212.80
Purchase #4	$39.86	7.360%	$42.7937	$42.79	$42.80	$42.80
Purchase #5	$184.42	13.700%	$209.6855	$209.69	$209.70	$209.70
Purchase #6	$141.45	12.841%	$159.6136	$159.61	$159.60	$159.60
Purchase #7	$131.78	10.377%	$145.4548	$145.45	$145.45	$145.50
7 purchase totals =	$816.06		$910.7806	$910.77	$910.80	$910.90