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	$10.37	10.276%	$11.4356	$11.44	$11.45	$11.40
Purchase #2	$78.47	13.493%	$89.058	$89.06	$89.05	$89.10
Purchase #3	$86.66	9.815%	$95.1657	$95.17	$95.15	$95.20
Purchase #4	$87.58	10.648%	$96.9055	$96.91	$96.90	$96.90
Purchase #5	$177.87	8.382%	$192.7791	$192.78	$192.80	$192.80
Purchase #6	$185.70	6.760%	$198.2533	$198.25	$198.25	$198.30
Purchase #7	$85.99	3.674%	$89.1493	$89.15	$89.15	$89.10
7 purchase totals =	$712.64		$772.7465	$772.76	$772.75	$772.80