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	$46.89	13.731%	$53.3285	$53.33	$53.35	$53.30
Purchase #2	$85.36	7.570%	$91.8218	$91.82	$91.80	$91.80
Purchase #3	$76.72	11.264%	$85.3617	$85.36	$85.35	$85.40
Purchase #4	$99.46	6.531%	$105.9557	$105.96	$105.95	$106.00
Purchase #5	$110.54	11.411%	$123.1537	$123.15	$123.15	$123.20
Purchase #6	$196.93	11.792%	$220.152	$220.15	$220.15	$220.20
Purchase #7	$242.63	9.314%	$265.2286	$265.23	$265.25	$265.20
7 purchase totals =	$858.53		$945.0020	$945.00	$945.00	$945.10