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	$86.34	13.775%	$98.2333	$98.23	$98.25	$98.20
Purchase #2	$22.99	11.424%	$25.6164	$25.62	$25.60	$25.60
Purchase #3	$64.54	11.811%	$72.1628	$72.16	$72.15	$72.20
Purchase #4	$172.46	9.688%	$189.1679	$189.17	$189.15	$189.20
Purchase #5	$167.85	10.525%	$185.5162	$185.52	$185.50	$185.50
Purchase #6	$10.27	12.430%	$11.5466	$11.55	$11.55	$11.50
Purchase #7	$29.26	11.591%	$32.6515	$32.65	$32.65	$32.70
7 purchase totals =	$553.71		$614.8947	$614.90	$614.85	$614.90