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	$199.54	7.562%	$214.6292	$214.63	$214.65	$214.60
Purchase #2	$91.63	13.144%	$103.6738	$103.67	$103.65	$103.70
Purchase #3	$90.49	6.766%	$96.6126	$96.61	$96.60	$96.60
Purchase #4	$117.32	10.858%	$130.0586	$130.06	$130.05	$130.10
Purchase #5	$99.59	8.847%	$108.4007	$108.40	$108.40	$108.40
Purchase #6	$94.82	6.190%	$100.6894	$100.69	$100.70	$100.70
Purchase #7	$222.53	11.742%	$248.6595	$248.66	$248.65	$248.70
7 purchase totals =	$915.92		$1,002.7238	$1,002.72	$1,002.70	$1,002.80