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	$90.59	8.612%	$98.3916	$98.39	$98.40	$98.40
Purchase #2	$123.50	13.469%	$140.1342	$140.13	$140.15	$140.10
Purchase #3	$54.49	12.410%	$61.2522	$61.25	$61.25	$61.30
Purchase #4	$151.87	6.531%	$161.7886	$161.79	$161.80	$161.80
Purchase #5	$207.80	11.231%	$231.138	$231.14	$231.15	$231.10
Purchase #6	$95.52	5.209%	$100.4956	$100.50	$100.50	$100.50
Purchase #7	$160.90	4.361%	$167.9168	$167.92	$167.90	$167.90
7 purchase totals =	$884.67		$961.1170	$961.12	$961.15	$961.10