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	$130.35	7.104%	$139.6101	$139.61	$139.60	$139.60
Purchase #2	$112.26	10.180%	$123.6881	$123.69	$123.70	$123.70
Purchase #3	$233.56	9.121%	$254.863	$254.86	$254.85	$254.90
Purchase #4	$50.94	11.644%	$56.8715	$56.87	$56.85	$56.90
Purchase #5	$115.96	5.416%	$122.2404	$122.24	$122.25	$122.20
Purchase #6	$147.56	10.175%	$162.5742	$162.57	$162.55	$162.60
Purchase #7	$185.52	5.381%	$195.5028	$195.50	$195.50	$195.50
7 purchase totals =	$976.15		$1,055.3501	$1,055.34	$1,055.30	$1,055.40