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	$30.60	10.143%	$33.7038	$33.70	$33.70	$33.70
Purchase #2	$67.61	4.172%	$70.4307	$70.43	$70.45	$70.40
Purchase #3	$51.57	13.838%	$58.7063	$58.71	$58.70	$58.70
Purchase #4	$109.88	12.174%	$123.2568	$123.26	$123.25	$123.30
Purchase #5	$55.27	11.802%	$61.793	$61.79	$61.80	$61.80
Purchase #6	$63.89	10.781%	$70.778	$70.78	$70.80	$70.80
Purchase #7	$94.88	11.269%	$105.572	$105.57	$105.55	$105.60
7 purchase totals =	$473.70		$524.2406	$524.24	$524.25	$524.30