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	$33.71	4.587%	$35.2563	$35.26	$35.25	$35.30
Purchase #2	$7.65	8.379%	$8.291	$8.29	$8.30	$8.30
Purchase #3	$92.82	11.853%	$103.822	$103.82	$103.80	$103.80
Purchase #4	$146.28	9.723%	$160.5028	$160.50	$160.50	$160.50
Purchase #5	$191.86	7.471%	$206.1939	$206.19	$206.20	$206.20
Purchase #6	$246.90	5.140%	$259.5907	$259.59	$259.60	$259.60
Purchase #7	$226.98	13.187%	$256.9119	$256.91	$256.90	$256.90
7 purchase totals =	$946.20		$1,030.5686	$1,030.56	$1,030.55	$1,030.60