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	$209.31	3.818%	$217.3015	$217.30	$217.30	$217.30
Purchase #2	$120.67	5.509%	$127.3177	$127.32	$127.30	$127.30
Purchase #3	$130.43	9.271%	$142.5222	$142.52	$142.50	$142.50
Purchase #4	$169.38	3.360%	$175.0712	$175.07	$175.05	$175.10
Purchase #5	$59.29	3.358%	$61.281	$61.28	$61.30	$61.30
Purchase #6	$197.61	10.764%	$218.8807	$218.88	$218.90	$218.90
Purchase #7	$112.62	8.539%	$122.2366	$122.24	$122.25	$122.20
7 purchase totals =	$999.31		$1,064.6109	$1,064.61	$1,064.60	$1,064.60