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	$147.53	8.553%	$160.1482	$160.15	$160.15	$160.10
Purchase #2	$31.52	10.166%	$34.7243	$34.72	$34.70	$34.70
Purchase #3	$144.47	12.703%	$162.822	$162.82	$162.80	$162.80
Purchase #4	$220.89	9.336%	$241.5123	$241.51	$241.50	$241.50
Purchase #5	$211.41	3.290%	$218.3654	$218.37	$218.35	$218.40
Purchase #6	$71.83	9.382%	$78.5691	$78.57	$78.55	$78.60
Purchase #7	$221.63	9.457%	$242.5895	$242.59	$242.60	$242.60
7 purchase totals =	$1,049.28		$1,138.7308	$1,138.73	$1,138.65	$1,138.70