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	$33.69	6.479%	$35.8728	$35.87	$35.85	$35.90
Purchase #2	$142.52	10.823%	$157.9449	$157.94	$157.95	$157.90
Purchase #3	$81.80	12.343%	$91.8966	$91.90	$91.90	$91.90
Purchase #4	$172.40	9.733%	$189.1797	$189.18	$189.20	$189.20
Purchase #5	$221.77	3.673%	$229.9156	$229.92	$229.90	$229.90
Purchase #6	$111.75	6.510%	$119.0249	$119.02	$119.00	$119.00
Purchase #7	$160.31	13.208%	$181.4837	$181.48	$181.50	$181.50
7 purchase totals =	$924.24		$1,005.3182	$1,005.31	$1,005.30	$1,005.30