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	$229.48	6.735%	$244.9355	$244.94	$244.95	$244.90
Purchase #2	$60.27	5.123%	$63.3576	$63.36	$63.35	$63.40
Purchase #3	$242.55	11.613%	$270.7173	$270.72	$270.70	$270.70
Purchase #4	$69.33	13.476%	$78.6729	$78.67	$78.65	$78.70
Purchase #5	$39.98	9.689%	$43.8537	$43.85	$43.85	$43.90
Purchase #6	$247.50	13.709%	$281.4298	$281.43	$281.45	$281.40
Purchase #7	$161.38	8.105%	$174.4598	$174.46	$174.45	$174.50
7 purchase totals =	$1,050.49		$1,157.4266	$1,157.43	$1,157.40	$1,157.50