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	$247.31	5.764%	$261.5649	$261.56	$261.55	$261.60
Purchase #2	$158.55	12.775%	$178.8048	$178.80	$178.80	$178.80
Purchase #3	$111.40	11.444%	$124.1486	$124.15	$124.15	$124.10
Purchase #4	$159.31	5.459%	$168.0067	$168.01	$168.00	$168.00
Purchase #5	$127.78	11.564%	$142.5565	$142.56	$142.55	$142.60
Purchase #6	$69.81	12.504%	$78.539	$78.54	$78.55	$78.50
Purchase #7	$214.48	11.337%	$238.7956	$238.80	$238.80	$238.80
7 purchase totals =	$1,088.64		$1,192.4161	$1,192.42	$1,192.40	$1,192.40