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	$233.40	9.364%	$255.2556	$255.26	$255.25	$255.30
Purchase #2	$33.48	9.853%	$36.7788	$36.78	$36.80	$36.80
Purchase #3	$232.96	5.534%	$245.852	$245.85	$245.85	$245.90
Purchase #4	$240.43	5.845%	$254.4831	$254.48	$254.50	$254.50
Purchase #5	$158.58	5.871%	$167.8902	$167.89	$167.90	$167.90
Purchase #6	$48.26	7.823%	$52.0354	$52.04	$52.05	$52.00
Purchase #7	$244.31	11.788%	$273.1093	$273.11	$273.10	$273.10
7 purchase totals =	$1,191.42		$1,285.4044	$1,285.41	$1,285.45	$1,285.50