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	$141.56	8.746%	$153.9408	$153.94	$153.95	$153.90
Purchase #2	$153.61	7.424%	$165.014	$165.01	$165.00	$165.00
Purchase #3	$159.89	5.695%	$168.9957	$169.00	$169.00	$169.00
Purchase #4	$180.77	6.199%	$191.9759	$191.98	$192.00	$192.00
Purchase #5	$136.26	10.295%	$150.288	$150.29	$150.30	$150.30
Purchase #6	$66.45	9.541%	$72.79	$72.79	$72.80	$72.80
Purchase #7	$44.86	7.820%	$48.3681	$48.37	$48.35	$48.40
7 purchase totals =	$883.40		$951.3725	$951.38	$951.40	$951.40