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	$233.88	13.404%	$265.2293	$265.23	$265.25	$265.20
Purchase #2	$90.25	12.603%	$101.6242	$101.62	$101.60	$101.60
Purchase #3	$240.31	13.334%	$272.3529	$272.35	$272.35	$272.40
Purchase #4	$82.50	13.665%	$93.7736	$93.77	$93.75	$93.80
Purchase #5	$242.37	11.229%	$269.5857	$269.59	$269.60	$269.60
Purchase #6	$31.60	4.786%	$33.1124	$33.11	$33.10	$33.10
Purchase #7	$140.45	7.443%	$150.9037	$150.90	$150.90	$150.90
7 purchase totals =	$1,061.36		$1,186.5818	$1,186.57	$1,186.55	$1,186.60