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	$63.95	13.503%	$72.5852	$72.59	$72.60	$72.60
Purchase #2	$113.79	3.797%	$118.1106	$118.11	$118.10	$118.10
Purchase #3	$180.84	8.785%	$196.7268	$196.73	$196.75	$196.70
Purchase #4	$13.61	6.259%	$14.4618	$14.46	$14.45	$14.50
Purchase #5	$90.28	11.232%	$100.4202	$100.42	$100.40	$100.40
Purchase #6	$200.29	13.414%	$227.1569	$227.16	$227.15	$227.20
Purchase #7	$232.67	13.278%	$263.5639	$263.56	$263.55	$263.60
7 purchase totals =	$895.43		$993.0254	$993.03	$993.00	$993.10