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	$57.94	6.153%	$61.505	$61.51	$61.50	$61.50
Purchase #2	$133.35	5.869%	$141.1763	$141.18	$141.20	$141.20
Purchase #3	$103.62	8.435%	$112.3603	$112.36	$112.35	$112.40
Purchase #4	$90.25	6.301%	$95.9367	$95.94	$95.95	$95.90
Purchase #5	$96.49	13.560%	$109.574	$109.57	$109.55	$109.60
Purchase #6	$36.50	4.430%	$38.117	$38.12	$38.10	$38.10
Purchase #7	$184.87	10.630%	$204.5217	$204.52	$204.50	$204.50
7 purchase totals =	$703.02		$763.1910	$763.20	$763.15	$763.20