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	$188.46	7.517%	$202.6265	$202.63	$202.65	$202.60
Purchase #2	$118.79	10.467%	$131.2237	$131.22	$131.20	$131.20
Purchase #3	$26.28	7.287%	$28.195	$28.20	$28.20	$28.20
Purchase #4	$137.55	4.215%	$143.3477	$143.35	$143.35	$143.30
Purchase #5	$220.83	13.612%	$250.8894	$250.89	$250.90	$250.90
Purchase #6	$71.78	12.270%	$80.5874	$80.59	$80.60	$80.60
Purchase #7	$164.71	6.196%	$174.9154	$174.92	$174.90	$174.90
7 purchase totals =	$928.40		$1,011.7851	$1,011.80	$1,011.80	$1,011.70