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	$123.60	8.675%	$134.3223	$134.32	$134.30	$134.30
Purchase #2	$192.44	4.103%	$200.3358	$200.34	$200.35	$200.30
Purchase #3	$29.49	7.472%	$31.6935	$31.69	$31.70	$31.70
Purchase #4	$194.73	10.651%	$215.4707	$215.47	$215.45	$215.50
Purchase #5	$34.79	8.447%	$37.7287	$37.73	$37.75	$37.70
Purchase #6	$94.79	13.742%	$107.816	$107.82	$107.80	$107.80
Purchase #7	$32.46	10.572%	$35.8917	$35.89	$35.90	$35.90
7 purchase totals =	$702.30		$763.2587	$763.26	$763.25	$763.20