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	$146.98	10.375%	$162.2292	$162.23	$162.25	$162.20
Purchase #2	$161.71	6.493%	$172.2098	$172.21	$172.20	$172.20
Purchase #3	$57.65	6.669%	$61.4947	$61.49	$61.50	$61.50
Purchase #4	$208.73	7.289%	$223.9443	$223.94	$223.95	$223.90
Purchase #5	$170.99	5.294%	$180.0422	$180.04	$180.05	$180.00
Purchase #6	$228.30	9.803%	$250.6802	$250.68	$250.70	$250.70
Purchase #7	$46.69	6.788%	$49.8593	$49.86	$49.85	$49.90
7 purchase totals =	$1,021.05		$1,100.4597	$1,100.45	$1,100.50	$1,100.40