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	$50.78	4.682%	$53.1575	$53.16	$53.15	$53.20
Purchase #2	$12.89	5.164%	$13.5556	$13.56	$13.55	$13.60
Purchase #3	$98.90	8.459%	$107.266	$107.27	$107.25	$107.30
Purchase #4	$221.64	3.517%	$229.4351	$229.44	$229.45	$229.40
Purchase #5	$134.43	12.311%	$150.9797	$150.98	$151.00	$151.00
Purchase #6	$70.83	8.221%	$76.6529	$76.65	$76.65	$76.70
Purchase #7	$250.38	3.222%	$258.4472	$258.45	$258.45	$258.40
7 purchase totals =	$839.85		$889.4940	$889.51	$889.50	$889.60