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	$40.72	4.740%	$42.6501	$42.65	$42.65	$42.70
Purchase #2	$79.97	4.322%	$83.4263	$83.43	$83.45	$83.40
Purchase #3	$111.62	4.769%	$116.9432	$116.94	$116.95	$116.90
Purchase #4	$244.49	8.387%	$264.9954	$265.00	$265.00	$265.00
Purchase #5	$200.81	4.252%	$209.3484	$209.35	$209.35	$209.30
Purchase #6	$167.84	9.768%	$184.2346	$184.23	$184.25	$184.20
Purchase #7	$107.96	5.842%	$114.267	$114.27	$114.25	$114.30
7 purchase totals =	$953.41		$1,015.8650	$1,015.87	$1,015.90	$1,015.80