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	$153.49	4.843%	$160.9235	$160.92	$160.90	$160.90
Purchase #2	$67.63	8.569%	$73.4252	$73.43	$73.45	$73.40
Purchase #3	$166.41	7.510%	$178.9074	$178.91	$178.90	$178.90
Purchase #4	$233.52	10.817%	$258.7799	$258.78	$258.80	$258.80
Purchase #5	$201.82	10.491%	$222.9929	$222.99	$223.00	$223.00
Purchase #6	$40.39	13.620%	$45.8911	$45.89	$45.90	$45.90
Purchase #7	$219.46	8.686%	$238.5223	$238.52	$238.50	$238.50
7 purchase totals =	$1,082.72		$1,179.4423	$1,179.44	$1,179.45	$1,179.40