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	$164.34	9.359%	$179.7206	$179.72	$179.70	$179.70
Purchase #2	$62.81	3.192%	$64.8149	$64.81	$64.80	$64.80
Purchase #3	$97.31	8.776%	$105.8499	$105.85	$105.85	$105.80
Purchase #4	$64.76	9.510%	$70.9187	$70.92	$70.90	$70.90
Purchase #5	$228.26	10.610%	$252.4784	$252.48	$252.50	$252.50
Purchase #6	$185.70	5.824%	$196.5152	$196.52	$196.50	$196.50
Purchase #7	$103.59	11.322%	$115.3185	$115.32	$115.30	$115.30
7 purchase totals =	$906.77		$985.6162	$985.62	$985.55	$985.50