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	$89.32	6.801%	$95.3947	$95.39	$95.40	$95.40
Purchase #2	$65.73	5.779%	$69.5285	$69.53	$69.55	$69.50
Purchase #3	$180.35	10.148%	$198.6519	$198.65	$198.65	$198.70
Purchase #4	$241.40	3.769%	$250.4984	$250.50	$250.50	$250.50
Purchase #5	$69.29	13.142%	$78.3961	$78.40	$78.40	$78.40
Purchase #6	$27.87	10.109%	$30.6874	$30.69	$30.70	$30.70
Purchase #7	$87.72	11.510%	$97.8166	$97.82	$97.80	$97.80
7 purchase totals =	$761.68		$820.9736	$820.98	$821.00	$821.00