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	$75.73	8.352%	$82.055	$82.06	$82.05	$82.10
Purchase #2	$42.36	11.124%	$47.0721	$47.07	$47.05	$47.10
Purchase #3	$160.88	13.476%	$182.5602	$182.56	$182.55	$182.60
Purchase #4	$135.93	13.469%	$154.2384	$154.24	$154.25	$154.20
Purchase #5	$18.86	7.256%	$20.2285	$20.23	$20.25	$20.20
Purchase #6	$190.72	13.170%	$215.8378	$215.84	$215.85	$215.80
Purchase #7	$130.98	11.450%	$145.9772	$145.98	$146.00	$146.00
7 purchase totals =	$755.46		$847.9692	$847.98	$848.00	$848.00