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	$133.51	11.349%	$148.662	$148.66	$148.65	$148.70
Purchase #2	$77.26	6.549%	$82.3198	$82.32	$82.30	$82.30
Purchase #3	$149.26	12.561%	$168.0085	$168.01	$168.00	$168.00
Purchase #4	$66.95	8.867%	$72.8865	$72.89	$72.90	$72.90
Purchase #5	$141.75	5.765%	$149.9219	$149.92	$149.90	$149.90
Purchase #6	$151.69	13.289%	$171.8481	$171.85	$171.85	$171.80
Purchase #7	$103.34	5.614%	$109.1415	$109.14	$109.15	$109.10
7 purchase totals =	$823.76		$902.7883	$902.79	$902.75	$902.70