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	$237.25	11.435%	$264.3795	$264.38	$264.40	$264.40
Purchase #2	$53.89	12.547%	$60.6516	$60.65	$60.65	$60.70
Purchase #3	$100.63	6.574%	$107.2454	$107.25	$107.25	$107.20
Purchase #4	$95.56	13.147%	$108.1233	$108.12	$108.10	$108.10
Purchase #5	$83.25	9.221%	$90.9265	$90.93	$90.95	$90.90
Purchase #6	$138.50	4.459%	$144.6757	$144.68	$144.70	$144.70
Purchase #7	$94.46	5.585%	$99.7356	$99.74	$99.75	$99.70
7 purchase totals =	$803.54		$875.7376	$875.75	$875.80	$875.70