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	$218.77	6.761%	$233.561	$233.56	$233.55	$233.60
Purchase #2	$80.88	10.450%	$89.332	$89.33	$89.35	$89.30
Purchase #3	$84.91	11.539%	$94.7078	$94.71	$94.70	$94.70
Purchase #4	$144.90	8.289%	$156.9108	$156.91	$156.90	$156.90
Purchase #5	$113.43	4.437%	$118.4629	$118.46	$118.45	$118.50
Purchase #6	$41.52	9.677%	$45.5379	$45.54	$45.55	$45.50
Purchase #7	$150.46	10.662%	$166.502	$166.50	$166.50	$166.50
7 purchase totals =	$834.87		$905.0144	$905.01	$905.00	$905.00