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	$33.89	13.865%	$38.5888	$38.59	$38.60	$38.60
Purchase #2	$43.91	4.646%	$45.9501	$45.95	$45.95	$46.00
Purchase #3	$85.39	3.173%	$88.0994	$88.10	$88.10	$88.10
Purchase #4	$49.94	12.809%	$56.3368	$56.34	$56.35	$56.30
Purchase #5	$65.92	8.678%	$71.6405	$71.64	$71.65	$71.60
Purchase #6	$227.71	6.385%	$242.2493	$242.25	$242.25	$242.20
Purchase #7	$31.96	11.201%	$35.5398	$35.54	$35.55	$35.50
7 purchase totals =	$538.72		$578.4047	$578.41	$578.45	$578.30