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	$187.48	6.691%	$200.0243	$200.02	$200.00	$200.00
Purchase #2	$144.37	12.497%	$162.4119	$162.41	$162.40	$162.40
Purchase #3	$192.46	10.572%	$212.8069	$212.81	$212.80	$212.80
Purchase #4	$216.58	5.526%	$228.5482	$228.55	$228.55	$228.50
Purchase #5	$116.92	5.591%	$123.457	$123.46	$123.45	$123.50
Purchase #6	$41.41	8.722%	$45.0218	$45.02	$45.00	$45.00
Purchase #7	$52.72	7.297%	$56.567	$56.57	$56.55	$56.60
7 purchase totals =	$951.94		$1,028.8371	$1,028.84	$1,028.75	$1,028.80