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	$231.51	3.221%	$238.9669	$238.97	$238.95	$239.00
Purchase #2	$206.90	7.418%	$222.2478	$222.25	$222.25	$222.20
Purchase #3	$91.49	4.454%	$95.565	$95.57	$95.55	$95.60
Purchase #4	$180.89	5.443%	$190.7358	$190.74	$190.75	$190.70
Purchase #5	$181.68	5.561%	$191.7832	$191.78	$191.80	$191.80
Purchase #6	$186.80	13.365%	$211.7658	$211.77	$211.75	$211.80
Purchase #7	$154.54	3.415%	$159.8175	$159.82	$159.80	$159.80
7 purchase totals =	$1,233.81		$1,310.8820	$1,310.90	$1,310.85	$1,310.90