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	$69.36	12.651%	$78.1347	$78.13	$78.15	$78.10
Purchase #2	$83.59	8.269%	$90.5021	$90.50	$90.50	$90.50
Purchase #3	$69.72	8.374%	$75.5584	$75.56	$75.55	$75.60
Purchase #4	$14.80	7.381%	$15.8924	$15.89	$15.90	$15.90
Purchase #5	$54.95	7.625%	$59.1399	$59.14	$59.15	$59.10
Purchase #6	$243.32	4.219%	$253.5857	$253.59	$253.60	$253.60
Purchase #7	$225.82	4.588%	$236.1806	$236.18	$236.20	$236.20
7 purchase totals =	$761.56		$808.9938	$808.99	$809.05	$809.00