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	$95.46	5.828%	$101.0234	$101.02	$101.00	$101.00
Purchase #2	$66.25	9.138%	$72.3039	$72.30	$72.30	$72.30
Purchase #3	$129.50	13.779%	$147.3438	$147.34	$147.35	$147.30
Purchase #4	$163.53	9.809%	$179.5707	$179.57	$179.55	$179.60
Purchase #5	$239.82	7.740%	$258.3821	$258.38	$258.40	$258.40
Purchase #6	$85.83	13.117%	$97.0883	$97.09	$97.10	$97.10
Purchase #7	$131.86	10.570%	$145.7976	$145.80	$145.80	$145.80
7 purchase totals =	$912.25		$1,001.5098	$1,001.50	$1,001.50	$1,001.50