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	$158.66	5.808%	$167.875	$167.88	$167.90	$167.90
Purchase #2	$55.81	3.726%	$57.8895	$57.89	$57.90	$57.90
Purchase #3	$156.81	7.757%	$168.9738	$168.97	$168.95	$169.00
Purchase #4	$249.49	7.490%	$268.1768	$268.18	$268.20	$268.20
Purchase #5	$26.96	10.243%	$29.7215	$29.72	$29.70	$29.70
Purchase #6	$74.35	11.479%	$82.8846	$82.88	$82.90	$82.90
Purchase #7	$143.83	8.803%	$156.4914	$156.49	$156.50	$156.50
7 purchase totals =	$865.91		$932.0126	$932.01	$932.05	$932.10