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	$206.69	7.806%	$222.8242	$222.82	$222.80	$222.80
Purchase #2	$229.54	8.331%	$248.663	$248.66	$248.65	$248.70
Purchase #3	$89.70	12.361%	$100.7878	$100.79	$100.80	$100.80
Purchase #4	$249.49	6.578%	$265.9015	$265.90	$265.90	$265.90
Purchase #5	$42.34	6.652%	$45.1565	$45.16	$45.15	$45.20
Purchase #6	$60.84	10.131%	$67.0037	$67.00	$67.00	$67.00
Purchase #7	$134.55	8.829%	$146.4294	$146.43	$146.45	$146.40
7 purchase totals =	$1,013.15		$1,096.7661	$1,096.76	$1,096.75	$1,096.80