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	$74.25	11.654%	$82.9031	$82.90	$82.90	$82.90
Purchase #2	$53.86	9.874%	$59.1781	$59.18	$59.20	$59.20
Purchase #3	$68.52	5.400%	$72.2201	$72.22	$72.20	$72.20
Purchase #4	$72.62	6.793%	$77.5531	$77.55	$77.55	$77.60
Purchase #5	$80.94	13.623%	$91.9665	$91.97	$91.95	$92.00
Purchase #6	$224.69	11.363%	$250.2215	$250.22	$250.20	$250.20
Purchase #7	$13.92	4.455%	$14.5401	$14.54	$14.55	$14.50
7 purchase totals =	$588.80		$648.5825	$648.58	$648.55	$648.60