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	$40.45	7.695%	$43.5626	$43.56	$43.55	$43.60
Purchase #2	$205.68	11.363%	$229.0514	$229.05	$229.05	$229.10
Purchase #3	$28.59	13.303%	$32.3933	$32.39	$32.40	$32.40
Purchase #4	$122.29	7.116%	$130.9922	$130.99	$131.00	$131.00
Purchase #5	$43.67	12.390%	$49.0807	$49.08	$49.10	$49.10
Purchase #6	$195.40	10.469%	$215.8564	$215.86	$215.85	$215.90
Purchase #7	$233.25	4.546%	$243.8535	$243.85	$243.85	$243.90
7 purchase totals =	$869.33		$944.7901	$944.78	$944.80	$945.00