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	$239.32	9.789%	$262.747	$262.75	$262.75	$262.70
Purchase #2	$88.87	12.501%	$99.9796	$99.98	$100.00	$100.00
Purchase #3	$144.48	4.378%	$150.8053	$150.81	$150.80	$150.80
Purchase #4	$98.81	10.469%	$109.1544	$109.15	$109.15	$109.20
Purchase #5	$113.70	5.762%	$120.2514	$120.25	$120.25	$120.30
Purchase #6	$39.56	9.109%	$43.1635	$43.16	$43.15	$43.20
Purchase #7	$128.49	7.528%	$138.1627	$138.16	$138.15	$138.20
7 purchase totals =	$853.23		$924.2639	$924.26	$924.25	$924.40