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	$37.41	10.425%	$41.31	$41.31	$41.30	$41.30
Purchase #2	$26.51	5.339%	$27.9254	$27.93	$27.95	$27.90
Purchase #3	$131.76	9.457%	$144.2205	$144.22	$144.20	$144.20
Purchase #4	$78.89	8.650%	$85.714	$85.71	$85.70	$85.70
Purchase #5	$225.58	7.799%	$243.173	$243.17	$243.15	$243.20
Purchase #6	$168.30	13.431%	$190.9044	$190.90	$190.90	$190.90
Purchase #7	$66.83	7.753%	$72.0113	$72.01	$72.00	$72.00
7 purchase totals =	$735.28		$805.2586	$805.25	$805.20	$805.20