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	$211.39	12.506%	$237.8264	$237.83	$237.85	$237.80
Purchase #2	$69.84	3.465%	$72.26	$72.26	$72.25	$72.30
Purchase #3	$70.54	10.206%	$77.7393	$77.74	$77.75	$77.70
Purchase #4	$49.61	9.155%	$54.1518	$54.15	$54.15	$54.20
Purchase #5	$91.96	8.812%	$100.0635	$100.06	$100.05	$100.10
Purchase #6	$14.60	5.469%	$15.3985	$15.40	$15.40	$15.40
Purchase #7	$33.67	12.276%	$37.8033	$37.80	$37.80	$37.80
7 purchase totals =	$541.61		$595.2428	$595.24	$595.25	$595.30