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	$233.43	8.750%	$253.8551	$253.86	$253.85	$253.90
Purchase #2	$86.33	3.532%	$89.3792	$89.38	$89.40	$89.40
Purchase #3	$31.29	8.616%	$33.9859	$33.99	$34.00	$34.00
Purchase #4	$29.89	8.277%	$32.364	$32.36	$32.35	$32.40
Purchase #5	$228.31	11.215%	$253.915	$253.92	$253.90	$253.90
Purchase #6	$216.31	3.507%	$223.896	$223.90	$223.90	$223.90
Purchase #7	$216.46	6.319%	$230.1381	$230.14	$230.15	$230.10
7 purchase totals =	$1,042.02		$1,117.5333	$1,117.55	$1,117.55	$1,117.60