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	$200.66	11.444%	$223.6235	$223.62	$223.60	$223.60
Purchase #2	$94.36	6.820%	$100.7954	$100.80	$100.80	$100.80
Purchase #3	$54.98	13.442%	$62.3704	$62.37	$62.35	$62.40
Purchase #4	$194.72	9.474%	$213.1678	$213.17	$213.15	$213.20
Purchase #5	$187.81	12.714%	$211.6882	$211.69	$211.70	$211.70
Purchase #6	$54.74	5.181%	$57.5761	$57.58	$57.60	$57.60
Purchase #7	$20.86	12.472%	$23.4617	$23.46	$23.45	$23.50
7 purchase totals =	$808.13		$892.6831	$892.69	$892.65	$892.80