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	$86.94	3.311%	$89.8186	$89.82	$89.80	$89.80
Purchase #2	$214.54	9.594%	$235.123	$235.12	$235.10	$235.10
Purchase #3	$216.50	5.565%	$228.5482	$228.55	$228.55	$228.50
Purchase #4	$82.56	11.444%	$92.0082	$92.01	$92.00	$92.00
Purchase #5	$205.32	4.369%	$214.2904	$214.29	$214.30	$214.30
Purchase #6	$22.93	7.479%	$24.6449	$24.64	$24.65	$24.60
Purchase #7	$112.97	9.415%	$123.6061	$123.61	$123.60	$123.60
7 purchase totals =	$941.76		$1,008.0394	$1,008.04	$1,008.00	$1,007.90