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	$193.35	10.406%	$213.47	$213.47	$213.45	$213.50
Purchase #2	$197.37	6.853%	$210.8958	$210.90	$210.90	$210.90
Purchase #3	$142.60	4.817%	$149.469	$149.47	$149.45	$149.50
Purchase #4	$116.62	10.519%	$128.8873	$128.89	$128.90	$128.90
Purchase #5	$73.47	10.592%	$81.2519	$81.25	$81.25	$81.30
Purchase #6	$133.38	4.155%	$138.9219	$138.92	$138.90	$138.90
Purchase #7	$174.28	8.116%	$188.4246	$188.42	$188.40	$188.40
7 purchase totals =	$1,031.07		$1,111.3205	$1,111.32	$1,111.25	$1,111.40