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	$48.57	13.429%	$55.0925	$55.09	$55.10	$55.10
Purchase #2	$162.75	3.835%	$168.9915	$168.99	$169.00	$169.00
Purchase #3	$168.73	13.517%	$191.5372	$191.54	$191.55	$191.50
Purchase #4	$165.33	11.600%	$184.5083	$184.51	$184.50	$184.50
Purchase #5	$103.48	12.110%	$116.0114	$116.01	$116.00	$116.00
Purchase #6	$65.29	10.464%	$72.1219	$72.12	$72.10	$72.10
Purchase #7	$163.41	12.229%	$183.3934	$183.39	$183.40	$183.40
7 purchase totals =	$877.56		$971.6562	$971.65	$971.65	$971.60