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	$152.89	6.225%	$162.4074	$162.41	$162.40	$162.40
Purchase #2	$17.86	13.173%	$20.2127	$20.21	$20.20	$20.20
Purchase #3	$67.63	6.588%	$72.0855	$72.09	$72.10	$72.10
Purchase #4	$37.34	13.496%	$42.3794	$42.38	$42.40	$42.40
Purchase #5	$31.82	3.640%	$32.9782	$32.98	$33.00	$33.00
Purchase #6	$233.38	8.622%	$253.502	$253.50	$253.50	$253.50
Purchase #7	$224.96	10.613%	$248.835	$248.84	$248.85	$248.80
7 purchase totals =	$765.88		$832.4002	$832.41	$832.45	$832.40