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	$141.62	4.556%	$148.0722	$148.07	$148.05	$148.10
Purchase #2	$147.73	7.677%	$159.0712	$159.07	$159.05	$159.10
Purchase #3	$199.77	7.835%	$215.422	$215.42	$215.40	$215.40
Purchase #4	$82.74	11.315%	$92.102	$92.10	$92.10	$92.10
Purchase #5	$227.47	12.182%	$255.1804	$255.18	$255.20	$255.20
Purchase #6	$83.40	8.196%	$90.2355	$90.24	$90.25	$90.20
Purchase #7	$110.32	3.261%	$113.9175	$113.92	$113.90	$113.90
7 purchase totals =	$993.05		$1,074.0008	$1,074.00	$1,073.95	$1,074.00