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	$131.86	3.739%	$136.7902	$136.79	$136.80	$136.80
Purchase #2	$65.56	11.270%	$72.9486	$72.95	$72.95	$72.90
Purchase #3	$75.34	4.592%	$78.7996	$78.80	$78.80	$78.80
Purchase #4	$126.88	13.490%	$143.9961	$144.00	$144.00	$144.00
Purchase #5	$163.44	12.845%	$184.4339	$184.43	$184.45	$184.40
Purchase #6	$218.42	3.347%	$225.7305	$225.73	$225.75	$225.70
Purchase #7	$203.69	7.514%	$218.9953	$219.00	$219.00	$219.00
7 purchase totals =	$985.19		$1,061.6942	$1,061.70	$1,061.75	$1,061.60