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	$113.57	10.774%	$125.806	$125.81	$125.80	$125.80
Purchase #2	$183.95	6.731%	$196.3317	$196.33	$196.35	$196.30
Purchase #3	$249.59	3.166%	$257.492	$257.49	$257.50	$257.50
Purchase #4	$11.82	9.571%	$12.9513	$12.95	$12.95	$13.00
Purchase #5	$149.30	8.740%	$162.3488	$162.35	$162.35	$162.30
Purchase #6	$161.95	12.861%	$182.7784	$182.78	$182.80	$182.80
Purchase #7	$69.50	3.753%	$72.1083	$72.11	$72.10	$72.10
7 purchase totals =	$939.68		$1,009.8165	$1,009.82	$1,009.85	$1,009.80