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	$141.52	3.170%	$146.0062	$146.01	$146.00	$146.00
Purchase #2	$33.89	12.324%	$38.0666	$38.07	$38.05	$38.10
Purchase #3	$191.42	4.669%	$200.3574	$200.36	$200.35	$200.40
Purchase #4	$33.57	13.530%	$38.112	$38.11	$38.10	$38.10
Purchase #5	$247.44	12.552%	$278.4987	$278.50	$278.50	$278.50
Purchase #6	$147.35	4.422%	$153.8658	$153.87	$153.85	$153.90
Purchase #7	$29.76	11.217%	$33.0982	$33.10	$33.10	$33.10
7 purchase totals =	$824.95		$888.0049	$888.02	$887.95	$888.10