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	$204.73	11.661%	$228.6036	$228.60	$228.60	$228.60
Purchase #2	$65.48	8.499%	$71.0451	$71.05	$71.05	$71.00
Purchase #3	$152.87	10.810%	$169.3952	$169.40	$169.40	$169.40
Purchase #4	$246.73	4.772%	$258.504	$258.50	$258.50	$258.50
Purchase #5	$27.48	5.519%	$28.9966	$29.00	$29.00	$29.00
Purchase #6	$111.89	13.734%	$127.257	$127.26	$127.25	$127.30
Purchase #7	$142.31	13.850%	$162.0199	$162.02	$162.00	$162.00
7 purchase totals =	$951.49		$1,045.8214	$1,045.83	$1,045.80	$1,045.80