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	$68.48	6.767%	$73.114	$73.11	$73.10	$73.10
Purchase #2	$90.67	3.326%	$93.6857	$93.69	$93.70	$93.70
Purchase #3	$147.32	3.222%	$152.0667	$152.07	$152.05	$152.10
Purchase #4	$165.88	4.243%	$172.9183	$172.92	$172.90	$172.90
Purchase #5	$139.73	5.270%	$147.0938	$147.09	$147.10	$147.10
Purchase #6	$99.61	9.689%	$109.2612	$109.26	$109.25	$109.30
Purchase #7	$164.25	10.643%	$181.7311	$181.73	$181.75	$181.70
7 purchase totals =	$875.94		$929.8708	$929.87	$929.85	$929.90