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	$157.54	6.119%	$167.1799	$167.18	$167.20	$167.20
Purchase #2	$50.43	12.864%	$56.9173	$56.92	$56.90	$56.90
Purchase #3	$92.46	12.280%	$103.8141	$103.81	$103.80	$103.80
Purchase #4	$143.57	3.859%	$149.1104	$149.11	$149.10	$149.10
Purchase #5	$33.55	3.155%	$34.6085	$34.61	$34.60	$34.60
Purchase #6	$159.41	5.295%	$167.8508	$167.85	$167.85	$167.90
Purchase #7	$41.58	4.825%	$43.5862	$43.59	$43.60	$43.60
7 purchase totals =	$678.54		$723.0672	$723.07	$723.05	$723.10