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	$64.68	13.239%	$73.243	$73.24	$73.25	$73.20
Purchase #2	$43.45	5.424%	$45.8067	$45.81	$45.80	$45.80
Purchase #3	$58.25	13.688%	$66.2233	$66.22	$66.20	$66.20
Purchase #4	$68.98	13.819%	$78.5123	$78.51	$78.50	$78.50
Purchase #5	$213.97	4.244%	$223.0509	$223.05	$223.05	$223.10
Purchase #6	$92.28	7.189%	$98.914	$98.91	$98.90	$98.90
Purchase #7	$167.27	10.666%	$185.111	$185.11	$185.10	$185.10
7 purchase totals =	$708.88		$770.8612	$770.85	$770.80	$770.80