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	$142.39	9.145%	$155.4116	$155.41	$155.40	$155.40
Purchase #2	$168.33	9.597%	$184.4846	$184.48	$184.50	$184.50
Purchase #3	$39.81	4.565%	$41.6273	$41.63	$41.65	$41.60
Purchase #4	$224.48	13.824%	$255.5121	$255.51	$255.50	$255.50
Purchase #5	$170.77	6.286%	$181.5046	$181.50	$181.50	$181.50
Purchase #6	$146.34	8.235%	$158.3911	$158.39	$158.40	$158.40
Purchase #7	$58.58	9.252%	$63.9998	$64.00	$64.00	$64.00
7 purchase totals =	$950.70		$1,040.9311	$1,040.92	$1,040.95	$1,040.90