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	$48.98	7.790%	$52.7955	$52.80	$52.80	$52.80
Purchase #2	$166.63	7.721%	$179.4955	$179.50	$179.50	$179.50
Purchase #3	$64.34	5.589%	$67.936	$67.94	$67.95	$67.90
Purchase #4	$162.31	11.414%	$180.8361	$180.84	$180.85	$180.80
Purchase #5	$150.88	7.826%	$162.6879	$162.69	$162.70	$162.70
Purchase #6	$235.48	11.841%	$263.3632	$263.36	$263.35	$263.40
Purchase #7	$81.83	11.622%	$91.3403	$91.34	$91.35	$91.30
7 purchase totals =	$910.45		$998.4545	$998.47	$998.50	$998.40