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	$175.48	5.501%	$185.1332	$185.13	$185.15	$185.10
Purchase #2	$80.45	3.567%	$83.3197	$83.32	$83.30	$83.30
Purchase #3	$235.33	8.425%	$255.1566	$255.16	$255.15	$255.20
Purchase #4	$52.44	13.380%	$59.4565	$59.46	$59.45	$59.50
Purchase #5	$101.26	5.583%	$106.9133	$106.91	$106.90	$106.90
Purchase #6	$236.52	10.249%	$260.7609	$260.76	$260.75	$260.80
Purchase #7	$238.41	3.426%	$246.5779	$246.58	$246.60	$246.60
7 purchase totals =	$1,119.89		$1,197.3181	$1,197.32	$1,197.30	$1,197.40