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	$98.73	6.761%	$105.4051	$105.41	$105.40	$105.40
Purchase #2	$94.86	6.176%	$100.7186	$100.72	$100.70	$100.70
Purchase #3	$56.88	9.628%	$62.3564	$62.36	$62.35	$62.40
Purchase #4	$63.73	13.218%	$72.1538	$72.15	$72.15	$72.20
Purchase #5	$71.26	13.473%	$80.8609	$80.86	$80.85	$80.90
Purchase #6	$175.90	5.376%	$185.3564	$185.36	$185.35	$185.40
Purchase #7	$196.28	4.334%	$204.7868	$204.79	$204.80	$204.80
7 purchase totals =	$757.64		$811.6380	$811.65	$811.60	$811.80