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	$100.71	6.718%	$107.4757	$107.48	$107.50	$107.50
Purchase #2	$64.89	12.144%	$72.7702	$72.77	$72.75	$72.80
Purchase #3	$126.53	5.758%	$133.8156	$133.82	$133.80	$133.80
Purchase #4	$240.56	9.809%	$264.1565	$264.16	$264.15	$264.20
Purchase #5	$123.42	10.710%	$136.6383	$136.64	$136.65	$136.60
Purchase #6	$215.54	8.214%	$233.2445	$233.24	$233.25	$233.20
Purchase #7	$95.58	13.250%	$108.2444	$108.24	$108.25	$108.20
7 purchase totals =	$967.23		$1,056.3452	$1,056.35	$1,056.35	$1,056.30