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	$149.69	8.624%	$162.5993	$162.60	$162.60	$162.60
Purchase #2	$80.27	7.463%	$86.2606	$86.26	$86.25	$86.30
Purchase #3	$239.37	4.783%	$250.8191	$250.82	$250.80	$250.80
Purchase #4	$233.88	7.460%	$251.3274	$251.33	$251.35	$251.30
Purchase #5	$10.89	10.204%	$12.0012	$12.00	$12.00	$12.00
Purchase #6	$67.87	6.300%	$72.1458	$72.15	$72.15	$72.10
Purchase #7	$98.27	10.415%	$108.5048	$108.50	$108.50	$108.50
7 purchase totals =	$880.24		$943.6582	$943.66	$943.65	$943.60