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	$35.39	6.139%	$37.5626	$37.56	$37.55	$37.60
Purchase #2	$91.26	12.863%	$102.9988	$103.00	$103.00	$103.00
Purchase #3	$168.35	10.576%	$186.1547	$186.15	$186.15	$186.20
Purchase #4	$75.69	3.449%	$78.3005	$78.30	$78.30	$78.30
Purchase #5	$208.28	7.513%	$223.9281	$223.93	$223.95	$223.90
Purchase #6	$86.43	13.699%	$98.27	$98.27	$98.25	$98.30
Purchase #7	$20.91	12.466%	$23.5166	$23.52	$23.50	$23.50
7 purchase totals =	$686.31		$750.7313	$750.73	$750.70	$750.80