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	$72.94	6.847%	$77.9342	$77.93	$77.95	$77.90
Purchase #2	$130.55	10.642%	$144.4431	$144.44	$144.45	$144.40
Purchase #3	$168.67	7.662%	$181.5935	$181.59	$181.60	$181.60
Purchase #4	$67.97	7.786%	$73.2621	$73.26	$73.25	$73.30
Purchase #5	$82.70	9.574%	$90.6177	$90.62	$90.60	$90.60
Purchase #6	$187.58	4.798%	$196.5801	$196.58	$196.60	$196.60
Purchase #7	$17.89	8.871%	$19.477	$19.48	$19.50	$19.50
7 purchase totals =	$728.30		$783.9077	$783.90	$783.95	$783.90