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	$123.50	6.289%	$131.2669	$131.27	$131.25	$131.30
Purchase #2	$122.96	4.790%	$128.8498	$128.85	$128.85	$128.80
Purchase #3	$52.59	6.788%	$56.1598	$56.16	$56.15	$56.20
Purchase #4	$234.67	13.120%	$265.4587	$265.46	$265.45	$265.50
Purchase #5	$206.58	13.703%	$234.8877	$234.89	$234.90	$234.90
Purchase #6	$125.35	5.366%	$132.0763	$132.08	$132.10	$132.10
Purchase #7	$91.55	12.341%	$102.8482	$102.85	$102.85	$102.80
7 purchase totals =	$957.20		$1,051.5474	$1,051.56	$1,051.55	$1,051.60