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	$232.70	4.685%	$243.602	$243.60	$243.60	$243.60
Purchase #2	$118.68	13.151%	$134.2876	$134.29	$134.30	$134.30
Purchase #3	$209.33	13.221%	$237.0055	$237.01	$237.00	$237.00
Purchase #4	$76.97	11.200%	$85.5906	$85.59	$85.60	$85.60
Purchase #5	$155.56	8.490%	$168.767	$168.77	$168.75	$168.80
Purchase #6	$146.75	13.873%	$167.1086	$167.11	$167.10	$167.10
Purchase #7	$100.50	10.586%	$111.1389	$111.14	$111.15	$111.10
7 purchase totals =	$1,040.49		$1,147.5002	$1,147.51	$1,147.50	$1,147.50