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	$125.56	6.678%	$133.9449	$133.94	$133.95	$133.90
Purchase #2	$192.34	4.156%	$200.3337	$200.33	$200.35	$200.30
Purchase #3	$98.88	12.711%	$111.4486	$111.45	$111.45	$111.40
Purchase #4	$209.56	11.809%	$234.3069	$234.31	$234.30	$234.30
Purchase #5	$32.43	7.858%	$34.9783	$34.98	$35.00	$35.00
Purchase #6	$133.40	8.782%	$145.1152	$145.12	$145.10	$145.10
Purchase #7	$164.61	11.524%	$183.5797	$183.58	$183.60	$183.60
7 purchase totals =	$956.78		$1,043.7073	$1,043.71	$1,043.75	$1,043.60