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	$184.44	4.850%	$193.3853	$193.39	$193.40	$193.40
Purchase #2	$150.71	13.478%	$171.0227	$171.02	$171.00	$171.00
Purchase #3	$76.36	11.368%	$85.0406	$85.04	$85.05	$85.00
Purchase #4	$230.53	13.751%	$262.2302	$262.23	$262.25	$262.20
Purchase #5	$242.79	12.741%	$273.7239	$273.72	$273.70	$273.70
Purchase #6	$73.80	12.228%	$82.8243	$82.82	$82.80	$82.80
Purchase #7	$11.87	13.401%	$13.4607	$13.46	$13.45	$13.50
7 purchase totals =	$970.50		$1,081.6877	$1,081.68	$1,081.65	$1,081.60