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	$174.37	6.534%	$185.7633	$185.76	$185.75	$185.80
Purchase #2	$182.76	7.478%	$196.4268	$196.43	$196.45	$196.40
Purchase #3	$142.36	13.368%	$161.3907	$161.39	$161.40	$161.40
Purchase #4	$9.51	10.689%	$10.5265	$10.53	$10.55	$10.50
Purchase #5	$78.75	11.183%	$87.5566	$87.56	$87.55	$87.60
Purchase #6	$74.84	8.595%	$81.2725	$81.27	$81.25	$81.30
Purchase #7	$98.84	4.764%	$103.5487	$103.55	$103.55	$103.50
7 purchase totals =	$761.43		$826.4851	$826.49	$826.50	$826.50