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	$180.41	5.719%	$190.7276	$190.73	$190.75	$190.70
Purchase #2	$29.57	7.252%	$31.7144	$31.71	$31.70	$31.70
Purchase #3	$171.81	11.676%	$191.8705	$191.87	$191.85	$191.90
Purchase #4	$93.59	11.280%	$104.147	$104.15	$104.15	$104.10
Purchase #5	$173.30	7.420%	$186.1589	$186.16	$186.15	$186.20
Purchase #6	$62.61	4.559%	$65.4644	$65.46	$65.45	$65.50
Purchase #7	$42.86	4.685%	$44.868	$44.87	$44.85	$44.90
7 purchase totals =	$754.15		$814.9508	$814.95	$814.90	$815.00