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	$203.38	11.560%	$226.8907	$226.89	$226.90	$226.90
Purchase #2	$51.93	3.138%	$53.5596	$53.56	$53.55	$53.60
Purchase #3	$141.32	6.806%	$150.9382	$150.94	$150.95	$150.90
Purchase #4	$181.37	8.386%	$196.5797	$196.58	$196.60	$196.60
Purchase #5	$140.78	4.169%	$146.6491	$146.65	$146.65	$146.60
Purchase #6	$181.72	10.311%	$200.4571	$200.46	$200.45	$200.50
Purchase #7	$225.70	8.239%	$244.2954	$244.30	$244.30	$244.30
7 purchase totals =	$1,126.20		$1,219.3698	$1,219.38	$1,219.40	$1,219.40