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	$181.87	8.256%	$196.8852	$196.89	$196.90	$196.90
Purchase #2	$163.66	11.583%	$182.6167	$182.62	$182.60	$182.60
Purchase #3	$35.58	3.481%	$36.8185	$36.82	$36.80	$36.80
Purchase #4	$31.67	4.191%	$32.9973	$33.00	$33.00	$33.00
Purchase #5	$231.80	13.809%	$263.8093	$263.81	$263.80	$263.80
Purchase #6	$80.29	12.298%	$90.1641	$90.16	$90.15	$90.20
Purchase #7	$159.96	12.711%	$180.2925	$180.29	$180.30	$180.30
7 purchase totals =	$884.83		$983.5836	$983.59	$983.55	$983.60