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	$152.60	11.404%	$170.0025	$170.00	$170.00	$170.00
Purchase #2	$198.76	12.535%	$223.6746	$223.67	$223.65	$223.70
Purchase #3	$77.72	4.449%	$81.1778	$81.18	$81.20	$81.20
Purchase #4	$242.61	5.304%	$255.478	$255.48	$255.50	$255.50
Purchase #5	$180.67	6.412%	$192.2546	$192.25	$192.25	$192.30
Purchase #6	$14.70	4.117%	$15.3052	$15.31	$15.30	$15.30
Purchase #7	$61.27	8.412%	$66.424	$66.42	$66.40	$66.40
7 purchase totals =	$928.33		$1,004.3167	$1,004.31	$1,004.30	$1,004.40