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	$109.89	8.302%	$119.0131	$119.01	$119.00	$119.00
Purchase #2	$89.74	3.344%	$92.7409	$92.74	$92.75	$92.70
Purchase #3	$167.46	7.870%	$180.6391	$180.64	$180.65	$180.60
Purchase #4	$38.39	3.138%	$39.5947	$39.59	$39.60	$39.60
Purchase #5	$57.36	7.779%	$61.822	$61.82	$61.80	$61.80
Purchase #6	$111.85	10.656%	$123.7687	$123.77	$123.75	$123.80
Purchase #7	$234.94	12.330%	$263.9081	$263.91	$263.90	$263.90
7 purchase totals =	$809.63		$881.4866	$881.48	$881.45	$881.40