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	$94.67	13.524%	$107.4732	$107.47	$107.45	$107.50
Purchase #2	$68.50	8.537%	$74.3478	$74.35	$74.35	$74.30
Purchase #3	$76.71	12.731%	$86.476	$86.48	$86.50	$86.50
Purchase #4	$218.66	4.516%	$228.5347	$228.53	$228.55	$228.50
Purchase #5	$100.52	6.360%	$106.9131	$106.91	$106.90	$106.90
Purchase #6	$191.31	9.469%	$209.4251	$209.43	$209.45	$209.40
Purchase #7	$174.50	12.697%	$196.6563	$196.66	$196.65	$196.70
7 purchase totals =	$924.87		$1,009.8262	$1,009.83	$1,009.85	$1,009.80