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	$192.46	8.215%	$208.2706	$208.27	$208.25	$208.30
Purchase #2	$51.76	5.447%	$54.5794	$54.58	$54.60	$54.60
Purchase #3	$109.85	12.489%	$123.5692	$123.57	$123.55	$123.60
Purchase #4	$136.92	13.775%	$155.7807	$155.78	$155.80	$155.80
Purchase #5	$148.52	9.294%	$162.3234	$162.32	$162.30	$162.30
Purchase #6	$117.59	7.312%	$126.1882	$126.19	$126.20	$126.20
Purchase #7	$161.91	5.803%	$171.3056	$171.31	$171.30	$171.30
7 purchase totals =	$919.01		$1,002.0171	$1,002.02	$1,002.00	$1,002.10