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	$134.96	12.530%	$151.8705	$151.87	$151.85	$151.90
Purchase #2	$87.96	4.465%	$91.8874	$91.89	$91.90	$91.90
Purchase #3	$198.89	3.788%	$206.424	$206.42	$206.40	$206.40
Purchase #4	$183.48	11.321%	$204.2518	$204.25	$204.25	$204.30
Purchase #5	$75.91	13.109%	$85.861	$85.86	$85.85	$85.90
Purchase #6	$26.59	5.250%	$27.986	$27.99	$28.00	$28.00
Purchase #7	$159.52	9.459%	$174.609	$174.61	$174.60	$174.60
7 purchase totals =	$867.31		$942.8897	$942.89	$942.85	$943.00