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	$146.85	10.730%	$162.607	$162.61	$162.60	$162.60
Purchase #2	$79.49	12.234%	$89.2148	$89.21	$89.20	$89.20
Purchase #3	$175.27	8.664%	$190.4554	$190.46	$190.45	$190.50
Purchase #4	$84.28	7.314%	$90.4442	$90.44	$90.45	$90.40
Purchase #5	$133.48	9.199%	$145.7588	$145.76	$145.75	$145.80
Purchase #6	$79.67	3.718%	$82.6321	$82.63	$82.65	$82.60
Purchase #7	$176.33	8.253%	$190.8825	$190.88	$190.90	$190.90
7 purchase totals =	$875.37		$951.9948	$951.99	$952.00	$952.00