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	$102.36	8.874%	$111.4434	$111.44	$111.45	$111.40
Purchase #2	$102.31	3.150%	$105.5328	$105.53	$105.55	$105.50
Purchase #3	$67.89	6.341%	$72.1949	$72.19	$72.20	$72.20
Purchase #4	$35.31	9.485%	$38.6592	$38.66	$38.65	$38.70
Purchase #5	$5.48	7.692%	$5.9015	$5.90	$5.90	$5.90
Purchase #6	$89.76	13.779%	$102.128	$102.13	$102.15	$102.10
Purchase #7	$197.68	10.380%	$218.1992	$218.20	$218.20	$218.20
7 purchase totals =	$600.79		$654.0590	$654.05	$654.10	$654.00