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	$146.99	13.787%	$167.2555	$167.26	$167.25	$167.30
Purchase #2	$16.27	3.138%	$16.7806	$16.78	$16.80	$16.80
Purchase #3	$44.80	10.724%	$49.6044	$49.60	$49.60	$49.60
Purchase #4	$98.96	12.453%	$111.2835	$111.28	$111.30	$111.30
Purchase #5	$88.28	6.802%	$94.2848	$94.28	$94.30	$94.30
Purchase #6	$66.69	6.800%	$71.2249	$71.22	$71.20	$71.20
Purchase #7	$138.55	13.549%	$157.3221	$157.32	$157.30	$157.30
7 purchase totals =	$600.54		$667.7558	$667.74	$667.75	$667.80