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	$164.96	13.727%	$187.6041	$187.60	$187.60	$187.60
Purchase #2	$150.72	13.844%	$171.5857	$171.59	$171.60	$171.60
Purchase #3	$185.41	5.315%	$195.2645	$195.26	$195.25	$195.30
Purchase #4	$183.97	7.664%	$198.0695	$198.07	$198.05	$198.10
Purchase #5	$192.76	10.667%	$213.3217	$213.32	$213.30	$213.30
Purchase #6	$245.71	8.412%	$266.3791	$266.38	$266.40	$266.40
Purchase #7	$243.37	10.224%	$268.2521	$268.25	$268.25	$268.30
7 purchase totals =	$1,366.90		$1,500.4767	$1,500.47	$1,500.45	$1,500.60