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	$166.32	7.712%	$179.1466	$179.15	$179.15	$179.10
Purchase #2	$225.77	7.738%	$243.2401	$243.24	$243.25	$243.20
Purchase #3	$97.45	11.264%	$108.4268	$108.43	$108.45	$108.40
Purchase #4	$232.87	10.413%	$257.1188	$257.12	$257.10	$257.10
Purchase #5	$156.75	4.155%	$163.263	$163.26	$163.25	$163.30
Purchase #6	$37.53	13.542%	$42.6123	$42.61	$42.60	$42.60
Purchase #7	$81.44	11.520%	$90.8219	$90.82	$90.80	$90.80
7 purchase totals =	$998.13		$1,084.6295	$1,084.63	$1,084.60	$1,084.50