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	$75.64	10.346%	$83.4657	$83.47	$83.45	$83.50
Purchase #2	$141.47	7.459%	$152.0222	$152.02	$152.00	$152.00
Purchase #3	$209.37	12.843%	$236.2594	$236.26	$236.25	$236.30
Purchase #4	$239.73	4.618%	$250.8007	$250.80	$250.80	$250.80
Purchase #5	$100.91	4.147%	$105.0947	$105.09	$105.10	$105.10
Purchase #6	$153.45	7.160%	$164.437	$164.44	$164.45	$164.40
Purchase #7	$117.71	11.534%	$131.2867	$131.29	$131.30	$131.30
7 purchase totals =	$1,038.28		$1,123.3664	$1,123.37	$1,123.35	$1,123.40