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	$146.78	3.570%	$152.02	$152.02	$152.00	$152.00
Purchase #2	$63.74	8.722%	$69.2994	$69.30	$69.30	$69.30
Purchase #3	$250.92	11.467%	$279.693	$279.69	$279.70	$279.70
Purchase #4	$54.71	5.327%	$57.6244	$57.62	$57.60	$57.60
Purchase #5	$164.96	12.152%	$185.0059	$185.01	$185.00	$185.00
Purchase #6	$141.56	13.503%	$160.6748	$160.67	$160.65	$160.70
Purchase #7	$141.70	10.607%	$156.7301	$156.73	$156.75	$156.70
7 purchase totals =	$964.37		$1,061.0476	$1,061.04	$1,061.00	$1,061.00