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	$218.66	9.573%	$239.5923	$239.59	$239.60	$239.60
Purchase #2	$237.73	5.660%	$251.1855	$251.19	$251.20	$251.20
Purchase #3	$64.77	13.518%	$73.5256	$73.53	$73.55	$73.50
Purchase #4	$47.87	7.535%	$51.477	$51.48	$51.50	$51.50
Purchase #5	$33.73	9.658%	$36.9876	$36.99	$37.00	$37.00
Purchase #6	$85.39	4.784%	$89.4751	$89.48	$89.50	$89.50
Purchase #7	$235.31	13.280%	$266.5592	$266.56	$266.55	$266.60
7 purchase totals =	$923.46		$1,008.8023	$1,008.82	$1,008.90	$1,008.90