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	$85.57	12.660%	$96.4032	$96.40	$96.40	$96.40
Purchase #2	$39.83	3.352%	$41.1651	$41.17	$41.15	$41.20
Purchase #3	$89.99	4.737%	$94.2528	$94.25	$94.25	$94.30
Purchase #4	$86.97	10.855%	$96.4106	$96.41	$96.40	$96.40
Purchase #5	$39.76	10.389%	$43.8907	$43.89	$43.90	$43.90
Purchase #6	$52.28	9.545%	$57.2701	$57.27	$57.25	$57.30
Purchase #7	$23.39	10.846%	$25.9269	$25.93	$25.95	$25.90
7 purchase totals =	$417.79		$455.3194	$455.32	$455.30	$455.40