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	$201.28	10.386%	$222.1849	$222.18	$222.20	$222.20
Purchase #2	$237.98	11.103%	$264.4029	$264.40	$264.40	$264.40
Purchase #3	$197.89	10.385%	$218.4409	$218.44	$218.45	$218.40
Purchase #4	$246.59	11.408%	$274.721	$274.72	$274.70	$274.70
Purchase #5	$161.79	3.525%	$167.4931	$167.49	$167.50	$167.50
Purchase #6	$122.96	3.356%	$127.0865	$127.09	$127.10	$127.10
Purchase #7	$35.35	5.832%	$37.4116	$37.41	$37.40	$37.40
7 purchase totals =	$1,203.84		$1,311.7409	$1,311.73	$1,311.75	$1,311.70