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	$144.74	7.731%	$155.9298	$155.93	$155.95	$155.90
Purchase #2	$49.98	8.610%	$54.2833	$54.28	$54.30	$54.30
Purchase #3	$151.64	3.774%	$157.3629	$157.36	$157.35	$157.40
Purchase #4	$233.29	11.845%	$260.9232	$260.92	$260.90	$260.90
Purchase #5	$150.40	11.300%	$167.3952	$167.40	$167.40	$167.40
Purchase #6	$234.83	6.806%	$250.8125	$250.81	$250.80	$250.80
Purchase #7	$98.69	5.276%	$103.8969	$103.90	$103.90	$103.90
7 purchase totals =	$1,063.57		$1,150.6038	$1,150.60	$1,150.60	$1,150.60