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	$90.76	4.466%	$94.8133	$94.81	$94.80	$94.80
Purchase #2	$177.70	7.787%	$191.5375	$191.54	$191.55	$191.50
Purchase #3	$87.82	13.776%	$99.9181	$99.92	$99.90	$99.90
Purchase #4	$172.84	9.393%	$189.0749	$189.07	$189.05	$189.10
Purchase #5	$167.33	8.721%	$181.9228	$181.92	$181.90	$181.90
Purchase #6	$56.76	4.258%	$59.1768	$59.18	$59.20	$59.20
Purchase #7	$172.48	8.752%	$187.5754	$187.58	$187.60	$187.60
7 purchase totals =	$925.69		$1,004.0188	$1,004.02	$1,004.00	$1,004.00