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	$219.66	11.285%	$244.4486	$244.45	$244.45	$244.40
Purchase #2	$86.45	3.321%	$89.321	$89.32	$89.30	$89.30
Purchase #3	$155.69	13.514%	$176.7299	$176.73	$176.75	$176.70
Purchase #4	$91.40	11.546%	$101.953	$101.95	$101.95	$102.00
Purchase #5	$25.90	7.166%	$27.756	$27.76	$27.75	$27.80
Purchase #6	$32.41	10.310%	$35.7515	$35.75	$35.75	$35.80
Purchase #7	$30.37	4.718%	$31.8029	$31.80	$31.80	$31.80
7 purchase totals =	$641.88		$707.7629	$707.76	$707.75	$707.80