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	$181.95	9.330%	$198.9259	$198.93	$198.95	$198.90
Purchase #2	$78.90	13.446%	$89.5089	$89.51	$89.50	$89.50
Purchase #3	$14.71	5.387%	$15.5024	$15.50	$15.50	$15.50
Purchase #4	$38.81	5.835%	$41.0746	$41.07	$41.05	$41.10
Purchase #5	$233.84	9.213%	$255.3837	$255.38	$255.40	$255.40
Purchase #6	$206.43	4.322%	$215.3519	$215.35	$215.35	$215.40
Purchase #7	$60.57	13.216%	$68.5749	$68.57	$68.55	$68.60
7 purchase totals =	$815.21		$884.3223	$884.31	$884.30	$884.40