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	$92.27	6.578%	$98.3395	$98.34	$98.35	$98.30
Purchase #2	$234.51	10.795%	$259.8254	$259.83	$259.85	$259.80
Purchase #3	$39.46	10.340%	$43.5402	$43.54	$43.55	$43.50
Purchase #4	$86.29	12.334%	$96.933	$96.93	$96.95	$96.90
Purchase #5	$141.76	13.735%	$161.2307	$161.23	$161.25	$161.20
Purchase #6	$27.36	13.604%	$31.0821	$31.08	$31.10	$31.10
Purchase #7	$65.77	8.115%	$71.1072	$71.11	$71.10	$71.10
7 purchase totals =	$687.42		$762.0581	$762.06	$762.15	$761.90