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	$172.39	11.577%	$192.3476	$192.35	$192.35	$192.30
Purchase #2	$235.62	10.522%	$260.4119	$260.41	$260.40	$260.40
Purchase #3	$235.89	5.745%	$249.4419	$249.44	$249.45	$249.40
Purchase #4	$72.68	6.662%	$77.5219	$77.52	$77.50	$77.50
Purchase #5	$150.98	12.535%	$169.9053	$169.91	$169.90	$169.90
Purchase #6	$94.35	9.585%	$103.3934	$103.39	$103.40	$103.40
Purchase #7	$31.61	4.405%	$33.0024	$33.00	$33.00	$33.00
7 purchase totals =	$993.52		$1,086.0244	$1,086.02	$1,086.00	$1,085.90