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	$177.32	4.297%	$184.9394	$184.94	$184.95	$184.90
Purchase #2	$234.39	5.444%	$247.1502	$247.15	$247.15	$247.20
Purchase #3	$193.40	7.669%	$208.2318	$208.23	$208.25	$208.20
Purchase #4	$146.30	13.807%	$166.4996	$166.50	$166.50	$166.50
Purchase #5	$124.59	12.821%	$140.5637	$140.56	$140.55	$140.60
Purchase #6	$169.72	9.438%	$185.7382	$185.74	$185.75	$185.70
Purchase #7	$150.99	11.156%	$167.8344	$167.83	$167.85	$167.80
7 purchase totals =	$1,196.71		$1,300.9573	$1,300.95	$1,301.00	$1,300.90