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	$165.84	4.842%	$173.87	$173.87	$173.85	$173.90
Purchase #2	$29.41	6.786%	$31.4058	$31.41	$31.40	$31.40
Purchase #3	$233.66	4.640%	$244.5018	$244.50	$244.50	$244.50
Purchase #4	$138.92	4.273%	$144.8561	$144.86	$144.85	$144.90
Purchase #5	$140.50	11.556%	$156.7362	$156.74	$156.75	$156.70
Purchase #6	$47.40	9.486%	$51.8964	$51.90	$51.90	$51.90
Purchase #7	$234.35	9.313%	$256.175	$256.18	$256.20	$256.20
7 purchase totals =	$990.08		$1,059.4413	$1,059.46	$1,059.45	$1,059.50