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	$31.26	5.446%	$32.9624	$32.96	$32.95	$33.00
Purchase #2	$167.25	9.191%	$182.6219	$182.62	$182.60	$182.60
Purchase #3	$100.70	12.344%	$113.1304	$113.13	$113.15	$113.10
Purchase #4	$230.83	4.816%	$241.9468	$241.95	$241.95	$241.90
Purchase #5	$108.92	6.818%	$116.3462	$116.35	$116.35	$116.30
Purchase #6	$19.33	7.853%	$20.848	$20.85	$20.85	$20.80
Purchase #7	$82.61	8.197%	$89.3815	$89.38	$89.40	$89.40
7 purchase totals =	$740.90		$797.2372	$797.24	$797.25	$797.10