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	$156.51	9.753%	$171.7744	$171.77	$171.75	$171.80
Purchase #2	$249.87	4.555%	$261.2516	$261.25	$261.25	$261.30
Purchase #3	$95.42	13.118%	$107.9372	$107.94	$107.95	$107.90
Purchase #4	$90.73	4.290%	$94.6223	$94.62	$94.60	$94.60
Purchase #5	$208.82	12.668%	$235.2733	$235.27	$235.25	$235.30
Purchase #6	$152.99	12.580%	$172.2361	$172.24	$172.25	$172.20
Purchase #7	$134.66	3.508%	$139.3839	$139.38	$139.40	$139.40
7 purchase totals =	$1,089.00		$1,182.4788	$1,182.47	$1,182.45	$1,182.50