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	$121.90	5.519%	$128.6277	$128.63	$128.65	$128.60
Purchase #2	$161.59	7.460%	$173.6446	$173.64	$173.65	$173.60
Purchase #3	$43.48	5.527%	$45.8831	$45.88	$45.90	$45.90
Purchase #4	$93.97	12.172%	$105.408	$105.41	$105.40	$105.40
Purchase #5	$238.86	6.282%	$253.8652	$253.87	$253.85	$253.90
Purchase #6	$50.86	7.849%	$54.852	$54.85	$54.85	$54.90
Purchase #7	$210.92	6.493%	$224.615	$224.62	$224.60	$224.60
7 purchase totals =	$921.58		$986.8956	$986.90	$986.90	$986.90