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	$116.82	11.482%	$130.2333	$130.23	$130.25	$130.20
Purchase #2	$215.60	13.393%	$244.4753	$244.48	$244.50	$244.50
Purchase #3	$46.76	10.816%	$51.8176	$51.82	$51.80	$51.80
Purchase #4	$75.66	4.197%	$78.8355	$78.84	$78.85	$78.80
Purchase #5	$92.32	13.764%	$105.0269	$105.03	$105.05	$105.00
Purchase #6	$211.40	10.142%	$232.8402	$232.84	$232.85	$232.80
Purchase #7	$170.60	4.848%	$178.8707	$178.87	$178.85	$178.90
7 purchase totals =	$929.16		$1,022.0995	$1,022.11	$1,022.15	$1,022.00