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	$226.86	6.444%	$241.4789	$241.48	$241.50	$241.50
Purchase #2	$233.79	6.341%	$248.6146	$248.61	$248.60	$248.60
Purchase #3	$241.99	13.200%	$273.9327	$273.93	$273.95	$273.90
Purchase #4	$31.91	12.749%	$35.9782	$35.98	$36.00	$36.00
Purchase #5	$41.75	9.305%	$45.6348	$45.63	$45.65	$45.60
Purchase #6	$37.81	11.404%	$42.1219	$42.12	$42.10	$42.10
Purchase #7	$117.66	6.640%	$125.4726	$125.47	$125.45	$125.50
7 purchase totals =	$931.77		$1,013.2337	$1,013.22	$1,013.25	$1,013.20