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	$46.57	11.696%	$52.0168	$52.02	$52.00	$52.00
Purchase #2	$162.38	5.361%	$171.0852	$171.09	$171.10	$171.10
Purchase #3	$90.77	5.168%	$95.461	$95.46	$95.45	$95.50
Purchase #4	$242.59	4.658%	$253.8898	$253.89	$253.90	$253.90
Purchase #5	$59.47	10.635%	$65.7946	$65.79	$65.80	$65.80
Purchase #6	$127.53	3.363%	$131.8188	$131.82	$131.80	$131.80
Purchase #7	$138.27	8.628%	$150.1999	$150.20	$150.20	$150.20
7 purchase totals =	$867.58		$920.2661	$920.27	$920.25	$920.30