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	$40.62	5.127%	$42.7026	$42.70	$42.70	$42.70
Purchase #2	$178.88	6.125%	$189.8364	$189.84	$189.85	$189.80
Purchase #3	$89.79	10.813%	$99.499	$99.50	$99.50	$99.50
Purchase #4	$112.80	9.549%	$123.5713	$123.57	$123.55	$123.60
Purchase #5	$74.59	5.860%	$78.961	$78.96	$78.95	$79.00
Purchase #6	$248.98	13.480%	$282.5425	$282.54	$282.55	$282.50
Purchase #7	$206.76	9.734%	$226.886	$226.89	$226.90	$226.90
7 purchase totals =	$952.42		$1,043.9988	$1,044.00	$1,044.00	$1,044.00