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	$99.46	10.295%	$109.6994	$109.70	$109.70	$109.70
Purchase #2	$165.63	5.364%	$174.5144	$174.51	$174.50	$174.50
Purchase #3	$83.61	7.329%	$89.7378	$89.74	$89.75	$89.70
Purchase #4	$46.29	12.826%	$52.2272	$52.23	$52.25	$52.20
Purchase #5	$223.53	6.439%	$237.9231	$237.92	$237.90	$237.90
Purchase #6	$237.54	8.712%	$258.2345	$258.23	$258.25	$258.20
Purchase #7	$98.69	7.261%	$105.8559	$105.86	$105.85	$105.90
7 purchase totals =	$954.75		$1,028.1923	$1,028.19	$1,028.20	$1,028.10