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	$81.48	6.375%	$86.6744	$86.67	$86.65	$86.70
Purchase #2	$211.56	10.359%	$233.4755	$233.48	$233.50	$233.50
Purchase #3	$17.87	3.259%	$18.4524	$18.45	$18.45	$18.50
Purchase #4	$50.76	3.356%	$52.4635	$52.46	$52.45	$52.50
Purchase #5	$101.34	3.436%	$104.822	$104.82	$104.80	$104.80
Purchase #6	$5.99	5.632%	$6.3274	$6.33	$6.35	$6.30
Purchase #7	$70.92	11.125%	$78.8099	$78.81	$78.80	$78.80
7 purchase totals =	$539.92		$581.0251	$581.02	$581.00	$581.10