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	$40.40	7.251%	$43.3294	$43.33	$43.35	$43.30
Purchase #2	$244.33	11.158%	$271.5923	$271.59	$271.60	$271.60
Purchase #3	$210.74	3.674%	$218.4826	$218.48	$218.50	$218.50
Purchase #4	$231.88	8.364%	$251.2744	$251.27	$251.25	$251.30
Purchase #5	$70.45	9.136%	$76.8863	$76.89	$76.90	$76.90
Purchase #6	$53.56	6.313%	$56.9412	$56.94	$56.95	$56.90
Purchase #7	$226.91	9.652%	$248.8114	$248.81	$248.80	$248.80
7 purchase totals =	$1,078.27		$1,167.3176	$1,167.31	$1,167.35	$1,167.30