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	$244.74	5.803%	$258.9423	$258.94	$258.95	$258.90
Purchase #2	$191.83	4.653%	$200.7558	$200.76	$200.75	$200.80
Purchase #3	$203.80	3.722%	$211.3854	$211.39	$211.40	$211.40
Purchase #4	$198.29	11.786%	$221.6605	$221.66	$221.65	$221.70
Purchase #5	$90.31	11.595%	$100.7814	$100.78	$100.80	$100.80
Purchase #6	$164.33	12.405%	$184.7151	$184.72	$184.70	$184.70
Purchase #7	$145.79	9.206%	$159.2114	$159.21	$159.20	$159.20
7 purchase totals =	$1,239.09		$1,337.4519	$1,337.46	$1,337.45	$1,337.50