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	$67.65	7.809%	$72.9328	$72.93	$72.95	$72.90
Purchase #2	$121.89	3.815%	$126.5401	$126.54	$126.55	$126.50
Purchase #3	$198.87	11.106%	$220.9565	$220.96	$220.95	$221.00
Purchase #4	$92.87	10.290%	$102.4263	$102.43	$102.45	$102.40
Purchase #5	$188.73	4.678%	$197.5588	$197.56	$197.55	$197.60
Purchase #6	$142.81	7.675%	$153.7707	$153.77	$153.75	$153.80
Purchase #7	$205.72	10.155%	$226.6109	$226.61	$226.60	$226.60
7 purchase totals =	$1,018.54		$1,100.7961	$1,100.80	$1,100.80	$1,100.80