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	$208.53	10.864%	$231.1847	$231.18	$231.20	$231.20
Purchase #2	$98.94	10.848%	$109.673	$109.67	$109.65	$109.70
Purchase #3	$120.60	7.733%	$129.926	$129.93	$129.95	$129.90
Purchase #4	$80.48	12.275%	$90.3589	$90.36	$90.35	$90.40
Purchase #5	$247.27	7.642%	$266.1664	$266.17	$266.15	$266.20
Purchase #6	$91.57	9.851%	$100.5906	$100.59	$100.60	$100.60
Purchase #7	$84.84	13.843%	$96.5844	$96.58	$96.60	$96.60
7 purchase totals =	$932.23		$1,024.4840	$1,024.48	$1,024.50	$1,024.60