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	$108.56	7.197%	$116.3731	$116.37	$116.35	$116.40
Purchase #2	$105.30	13.199%	$119.1985	$119.20	$119.20	$119.20
Purchase #3	$106.89	12.155%	$119.8825	$119.88	$119.90	$119.90
Purchase #4	$111.37	12.865%	$125.6978	$125.70	$125.70	$125.70
Purchase #5	$90.59	9.752%	$99.4243	$99.42	$99.40	$99.40
Purchase #6	$248.29	10.129%	$273.4393	$273.44	$273.45	$273.40
Purchase #7	$149.83	6.291%	$159.2558	$159.26	$159.25	$159.30
7 purchase totals =	$920.83		$1,013.2713	$1,013.27	$1,013.25	$1,013.30