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	$117.51	9.603%	$128.7945	$128.79	$128.80	$128.80
Purchase #2	$6.43	13.515%	$7.299	$7.30	$7.30	$7.30
Purchase #3	$83.47	7.410%	$89.6551	$89.66	$89.65	$89.70
Purchase #4	$64.78	6.811%	$69.1922	$69.19	$69.20	$69.20
Purchase #5	$224.25	6.673%	$239.2142	$239.21	$239.20	$239.20
Purchase #6	$105.42	10.305%	$116.2835	$116.28	$116.30	$116.30
Purchase #7	$73.79	11.705%	$82.4271	$82.43	$82.45	$82.40
7 purchase totals =	$675.65		$732.8656	$732.86	$732.90	$732.90