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	$162.59	10.348%	$179.4148	$179.41	$179.40	$179.40
Purchase #2	$26.62	10.264%	$29.3523	$29.35	$29.35	$29.40
Purchase #3	$213.46	12.778%	$240.7359	$240.74	$240.75	$240.70
Purchase #4	$82.36	8.387%	$89.2675	$89.27	$89.25	$89.30
Purchase #5	$76.32	5.460%	$80.4871	$80.49	$80.50	$80.50
Purchase #6	$199.99	9.244%	$218.4771	$218.48	$218.50	$218.50
Purchase #7	$194.98	6.759%	$208.1587	$208.16	$208.15	$208.20
7 purchase totals =	$956.32		$1,045.8934	$1,045.90	$1,045.90	$1,046.00