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	$229.40	8.797%	$249.5803	$249.58	$249.60	$249.60
Purchase #2	$41.53	3.626%	$43.0359	$43.04	$43.05	$43.00
Purchase #3	$219.81	6.250%	$233.5481	$233.55	$233.55	$233.50
Purchase #4	$75.64	7.845%	$81.574	$81.57	$81.55	$81.60
Purchase #5	$36.82	13.766%	$41.8886	$41.89	$41.90	$41.90
Purchase #6	$118.44	7.460%	$127.2756	$127.28	$127.30	$127.30
Purchase #7	$222.53	4.168%	$231.8051	$231.81	$231.80	$231.80
7 purchase totals =	$944.17		$1,008.7076	$1,008.72	$1,008.75	$1,008.70