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	$124.92	7.535%	$134.3327	$134.33	$134.35	$134.30
Purchase #2	$172.86	13.701%	$196.5435	$196.54	$196.55	$196.50
Purchase #3	$216.26	10.266%	$238.4613	$238.46	$238.45	$238.50
Purchase #4	$202.76	7.823%	$218.6219	$218.62	$218.60	$218.60
Purchase #5	$98.70	11.774%	$110.3209	$110.32	$110.30	$110.30
Purchase #6	$202.35	4.741%	$211.9434	$211.94	$211.95	$211.90
Purchase #7	$88.88	11.468%	$99.0728	$99.07	$99.05	$99.10
7 purchase totals =	$1,106.73		$1,209.2965	$1,209.28	$1,209.25	$1,209.20