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	$227.90	10.502%	$251.8341	$251.83	$251.85	$251.80
Purchase #2	$244.41	12.427%	$274.7828	$274.78	$274.80	$274.80
Purchase #3	$70.77	7.454%	$76.0452	$76.05	$76.05	$76.00
Purchase #4	$99.95	12.363%	$112.3068	$112.31	$112.30	$112.30
Purchase #5	$92.33	9.155%	$100.7828	$100.78	$100.80	$100.80
Purchase #6	$243.59	9.722%	$267.2718	$267.27	$267.25	$267.30
Purchase #7	$74.71	10.148%	$82.2916	$82.29	$82.30	$82.30
7 purchase totals =	$1,053.66		$1,165.3151	$1,165.31	$1,165.35	$1,165.30