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	$187.50	10.686%	$207.5363	$207.54	$207.55	$207.50
Purchase #2	$114.92	4.198%	$119.7443	$119.74	$119.75	$119.70
Purchase #3	$75.52	3.293%	$78.0069	$78.01	$78.00	$78.00
Purchase #4	$52.98	13.202%	$59.9744	$59.97	$59.95	$60.00
Purchase #5	$149.72	4.106%	$155.8675	$155.87	$155.85	$155.90
Purchase #6	$135.86	12.186%	$152.4159	$152.42	$152.40	$152.40
Purchase #7	$95.83	5.212%	$100.8247	$100.82	$100.80	$100.80
7 purchase totals =	$812.33		$874.3700	$874.37	$874.30	$874.30