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	$69.29	4.744%	$72.5771	$72.58	$72.60	$72.60
Purchase #2	$7.31	12.472%	$8.2217	$8.22	$8.20	$8.20
Purchase #3	$178.47	8.472%	$193.59	$193.59	$193.60	$193.60
Purchase #4	$14.56	9.216%	$15.9018	$15.90	$15.90	$15.90
Purchase #5	$235.39	6.801%	$251.3989	$251.40	$251.40	$251.40
Purchase #6	$172.75	13.558%	$196.1714	$196.17	$196.15	$196.20
Purchase #7	$250.96	9.557%	$274.9442	$274.94	$274.95	$274.90
7 purchase totals =	$928.73		$1,012.8051	$1,012.80	$1,012.80	$1,012.80