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	$85.87	11.698%	$95.9151	$95.92	$95.90	$95.90
Purchase #2	$26.81	4.544%	$28.0282	$28.03	$28.05	$28.00
Purchase #3	$167.49	5.264%	$176.3067	$176.31	$176.30	$176.30
Purchase #4	$36.59	10.145%	$40.3021	$40.30	$40.30	$40.30
Purchase #5	$94.33	6.172%	$100.152	$100.15	$100.15	$100.20
Purchase #6	$147.29	3.806%	$152.8959	$152.90	$152.90	$152.90
Purchase #7	$194.75	9.474%	$213.2006	$213.20	$213.20	$213.20
7 purchase totals =	$753.13		$806.8006	$806.81	$806.80	$806.80