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	$7.28	7.763%	$7.8451	$7.85	$7.85	$7.80
Purchase #2	$92.48	13.859%	$105.2968	$105.30	$105.30	$105.30
Purchase #3	$167.93	4.742%	$175.8932	$175.89	$175.90	$175.90
Purchase #4	$101.73	6.571%	$108.4147	$108.41	$108.40	$108.40
Purchase #5	$28.77	10.790%	$31.8743	$31.87	$31.85	$31.90
Purchase #6	$105.27	8.253%	$113.9579	$113.96	$113.95	$114.00
Purchase #7	$199.45	5.543%	$210.5055	$210.51	$210.50	$210.50
7 purchase totals =	$702.91		$753.7875	$753.79	$753.75	$753.80