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	$216.85	11.623%	$242.0545	$242.05	$242.05	$242.10
Purchase #2	$80.72	8.626%	$87.6829	$87.68	$87.70	$87.70
Purchase #3	$122.62	13.872%	$139.6298	$139.63	$139.65	$139.60
Purchase #4	$135.91	12.202%	$152.4937	$152.49	$152.50	$152.50
Purchase #5	$111.52	13.555%	$126.6365	$126.64	$126.65	$126.60
Purchase #6	$117.34	11.198%	$130.4797	$130.48	$130.50	$130.50
Purchase #7	$116.33	6.458%	$123.8426	$123.84	$123.85	$123.80
7 purchase totals =	$901.29		$1,002.8197	$1,002.81	$1,002.90	$1,002.80