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	$62.50	8.477%	$67.7981	$67.80	$67.80	$67.80
Purchase #2	$56.31	4.835%	$59.0326	$59.03	$59.05	$59.00
Purchase #3	$86.30	7.254%	$92.5602	$92.56	$92.55	$92.60
Purchase #4	$212.54	9.343%	$232.3976	$232.40	$232.40	$232.40
Purchase #5	$126.37	8.170%	$136.6944	$136.69	$136.70	$136.70
Purchase #6	$72.34	8.135%	$78.2249	$78.22	$78.20	$78.20
Purchase #7	$131.93	8.827%	$143.5755	$143.58	$143.60	$143.60
7 purchase totals =	$748.29		$810.2833	$810.28	$810.30	$810.30