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	$14.85	4.251%	$15.4813	$15.48	$15.50	$15.50
Purchase #2	$105.70	5.329%	$111.3328	$111.33	$111.35	$111.30
Purchase #3	$48.34	5.711%	$51.1007	$51.10	$51.10	$51.10
Purchase #4	$246.26	11.133%	$273.6761	$273.68	$273.70	$273.70
Purchase #5	$168.68	9.780%	$185.1769	$185.18	$185.20	$185.20
Purchase #6	$5.34	13.650%	$6.0689	$6.07	$6.05	$6.10
Purchase #7	$37.29	11.481%	$41.5713	$41.57	$41.55	$41.60
7 purchase totals =	$626.46		$684.4080	$684.41	$684.45	$684.50