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	$162.30	3.208%	$167.5066	$167.51	$167.50	$167.50
Purchase #2	$14.54	4.145%	$15.1427	$15.14	$15.15	$15.10
Purchase #3	$18.35	4.155%	$19.1124	$19.11	$19.10	$19.10
Purchase #4	$71.71	7.473%	$77.0689	$77.07	$77.05	$77.10
Purchase #5	$91.57	11.524%	$102.1225	$102.12	$102.10	$102.10
Purchase #6	$28.95	13.318%	$32.8056	$32.81	$32.80	$32.80
Purchase #7	$37.46	10.732%	$41.4802	$41.48	$41.50	$41.50
7 purchase totals =	$424.88		$455.2389	$455.24	$455.20	$455.20