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	$61.63	3.382%	$63.7143	$63.71	$63.70	$63.70
Purchase #2	$237.56	13.290%	$269.1317	$269.13	$269.15	$269.10
Purchase #3	$103.41	13.611%	$117.4851	$117.49	$117.50	$117.50
Purchase #4	$37.89	11.801%	$42.3614	$42.36	$42.35	$42.40
Purchase #5	$58.60	12.304%	$65.8101	$65.81	$65.80	$65.80
Purchase #6	$238.83	5.623%	$252.2594	$252.26	$252.25	$252.30
Purchase #7	$122.59	7.503%	$131.7879	$131.79	$131.80	$131.80
7 purchase totals =	$860.51		$942.5499	$942.55	$942.55	$942.60