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	$90.89	8.343%	$98.473	$98.47	$98.45	$98.50
Purchase #2	$69.33	9.371%	$75.8269	$75.83	$75.85	$75.80
Purchase #3	$157.71	5.272%	$166.0245	$166.02	$166.00	$166.00
Purchase #4	$198.45	13.159%	$224.564	$224.56	$224.55	$224.60
Purchase #5	$53.28	11.190%	$59.242	$59.24	$59.25	$59.20
Purchase #6	$64.89	10.789%	$71.891	$71.89	$71.90	$71.90
Purchase #7	$52.66	13.860%	$59.9587	$59.96	$59.95	$60.00
7 purchase totals =	$687.21		$755.9801	$755.97	$755.95	$756.00