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	$227.28	7.597%	$244.5465	$244.55	$244.55	$244.50
Purchase #2	$39.43	8.439%	$42.7575	$42.76	$42.75	$42.80
Purchase #3	$189.61	5.696%	$200.4102	$200.41	$200.40	$200.40
Purchase #4	$181.36	13.551%	$205.9361	$205.94	$205.95	$205.90
Purchase #5	$83.93	3.722%	$87.0539	$87.05	$87.05	$87.10
Purchase #6	$172.27	12.691%	$194.1328	$194.13	$194.15	$194.10
Purchase #7	$37.51	10.181%	$41.3289	$41.33	$41.35	$41.30
7 purchase totals =	$931.39		$1,016.1659	$1,016.17	$1,016.20	$1,016.10