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	$163.35	3.273%	$168.6964	$168.70	$168.70	$168.70
Purchase #2	$182.32	7.635%	$196.2401	$196.24	$196.25	$196.20
Purchase #3	$57.76	3.442%	$59.7481	$59.75	$59.75	$59.70
Purchase #4	$172.59	11.199%	$191.9184	$191.92	$191.90	$191.90
Purchase #5	$154.36	11.194%	$171.6391	$171.64	$171.65	$171.60
Purchase #6	$78.70	3.630%	$81.5568	$81.56	$81.55	$81.60
Purchase #7	$196.92	8.163%	$212.9946	$212.99	$213.00	$213.00
7 purchase totals =	$1,006.00		$1,082.7935	$1,082.80	$1,082.80	$1,082.70