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	$144.95	13.441%	$164.4327	$164.43	$164.45	$164.40
Purchase #2	$44.67	7.743%	$48.1288	$48.13	$48.15	$48.10
Purchase #3	$143.31	6.172%	$152.1551	$152.16	$152.15	$152.20
Purchase #4	$89.82	9.425%	$98.2855	$98.29	$98.30	$98.30
Purchase #5	$215.88	7.586%	$232.2567	$232.26	$232.25	$232.30
Purchase #6	$143.40	11.320%	$159.6329	$159.63	$159.65	$159.60
Purchase #7	$172.64	13.526%	$195.9913	$195.99	$196.00	$196.00
7 purchase totals =	$954.67		$1,050.8830	$1,050.89	$1,050.95	$1,050.90