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	$139.66	4.766%	$146.3162	$146.32	$146.30	$146.30
Purchase #2	$232.27	4.715%	$243.2215	$243.22	$243.20	$243.20
Purchase #3	$170.79	12.526%	$192.1832	$192.18	$192.20	$192.20
Purchase #4	$101.51	3.161%	$104.7187	$104.72	$104.70	$104.70
Purchase #5	$190.63	5.625%	$201.3529	$201.35	$201.35	$201.40
Purchase #6	$65.39	10.799%	$72.4515	$72.45	$72.45	$72.50
Purchase #7	$73.36	6.683%	$78.2626	$78.26	$78.25	$78.30
7 purchase totals =	$973.61		$1,038.5066	$1,038.50	$1,038.45	$1,038.60