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	$99.44	10.389%	$109.7708	$109.77	$109.75	$109.80
Purchase #2	$211.83	9.629%	$232.2271	$232.23	$232.25	$232.20
Purchase #3	$45.54	4.379%	$47.5342	$47.53	$47.55	$47.50
Purchase #4	$103.73	5.844%	$109.792	$109.79	$109.80	$109.80
Purchase #5	$163.61	5.820%	$173.1321	$173.13	$173.15	$173.10
Purchase #6	$46.46	7.601%	$49.9914	$49.99	$50.00	$50.00
Purchase #7	$65.71	8.232%	$71.1192	$71.12	$71.10	$71.10
7 purchase totals =	$736.32		$793.5668	$793.56	$793.60	$793.50