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	$94.72	10.419%	$104.5889	$104.59	$104.60	$104.60
Purchase #2	$245.61	10.433%	$271.2345	$271.23	$271.25	$271.20
Purchase #3	$235.92	8.865%	$256.8343	$256.83	$256.85	$256.80
Purchase #4	$118.91	10.646%	$131.5692	$131.57	$131.55	$131.60
Purchase #5	$58.47	8.214%	$63.2727	$63.27	$63.25	$63.30
Purchase #6	$112.33	3.319%	$116.0582	$116.06	$116.05	$116.10
Purchase #7	$163.34	10.419%	$180.3584	$180.36	$180.35	$180.40
7 purchase totals =	$1,029.30		$1,123.9162	$1,123.91	$1,123.90	$1,124.00