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	$80.83	6.275%	$85.9021	$85.90	$85.90	$85.90
Purchase #2	$33.59	12.336%	$37.7337	$37.73	$37.75	$37.70
Purchase #3	$181.84	10.728%	$201.3478	$201.35	$201.35	$201.30
Purchase #4	$219.89	11.597%	$245.3906	$245.39	$245.40	$245.40
Purchase #5	$39.61	5.746%	$41.886	$41.89	$41.90	$41.90
Purchase #6	$31.98	6.687%	$34.1185	$34.12	$34.10	$34.10
Purchase #7	$59.94	11.769%	$66.9943	$66.99	$67.00	$67.00
7 purchase totals =	$647.68		$713.3730	$713.37	$713.40	$713.30