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	$164.85	9.592%	$180.6624	$180.66	$180.65	$180.70
Purchase #2	$21.98	4.296%	$22.9243	$22.92	$22.90	$22.90
Purchase #3	$95.30	13.590%	$108.2513	$108.25	$108.25	$108.30
Purchase #4	$250.43	8.823%	$272.5254	$272.53	$272.55	$272.50
Purchase #5	$228.80	5.236%	$240.78	$240.78	$240.80	$240.80
Purchase #6	$89.95	4.864%	$94.3252	$94.33	$94.35	$94.30
Purchase #7	$225.38	12.411%	$253.3519	$253.35	$253.35	$253.40
7 purchase totals =	$1,076.69		$1,172.8205	$1,172.82	$1,172.85	$1,172.90