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	$170.34	3.610%	$176.4893	$176.49	$176.50	$176.50
Purchase #2	$169.43	11.502%	$188.9178	$188.92	$188.90	$188.90
Purchase #3	$200.52	7.678%	$215.9159	$215.92	$215.90	$215.90
Purchase #4	$32.65	11.414%	$36.3767	$36.38	$36.40	$36.40
Purchase #5	$98.87	6.758%	$105.5516	$105.55	$105.55	$105.60
Purchase #6	$179.58	10.352%	$198.1701	$198.17	$198.15	$198.20
Purchase #7	$130.79	5.415%	$137.8723	$137.87	$137.85	$137.90
7 purchase totals =	$982.18		$1,059.2937	$1,059.30	$1,059.25	$1,059.40