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	$250.39	5.817%	$264.9552	$264.96	$264.95	$265.00
Purchase #2	$140.65	7.290%	$150.9034	$150.90	$150.90	$150.90
Purchase #3	$93.43	7.471%	$100.4102	$100.41	$100.40	$100.40
Purchase #4	$239.55	12.718%	$270.016	$270.02	$270.00	$270.00
Purchase #5	$244.58	4.780%	$256.2709	$256.27	$256.25	$256.30
Purchase #6	$52.84	12.546%	$59.4693	$59.47	$59.45	$59.50
Purchase #7	$211.75	5.628%	$223.6673	$223.67	$223.65	$223.70
7 purchase totals =	$1,233.19		$1,325.6923	$1,325.70	$1,325.60	$1,325.80