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	$207.50	12.391%	$233.2113	$233.21	$233.20	$233.20
Purchase #2	$20.83	3.764%	$21.614	$21.61	$21.60	$21.60
Purchase #3	$64.40	12.371%	$72.3669	$72.37	$72.35	$72.40
Purchase #4	$247.29	7.484%	$265.7972	$265.80	$265.80	$265.80
Purchase #5	$97.64	10.582%	$107.9723	$107.97	$107.95	$108.00
Purchase #6	$217.41	13.292%	$246.3081	$246.31	$246.30	$246.30
Purchase #7	$67.66	6.601%	$72.1262	$72.13	$72.15	$72.10
7 purchase totals =	$922.73		$1,019.3960	$1,019.40	$1,019.35	$1,019.40