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	$177.58	8.408%	$192.5109	$192.51	$192.50	$192.50
Purchase #2	$70.32	10.370%	$77.6122	$77.61	$77.60	$77.60
Purchase #3	$85.30	7.209%	$91.4493	$91.45	$91.45	$91.40
Purchase #4	$73.40	10.553%	$81.1459	$81.15	$81.15	$81.10
Purchase #5	$157.34	13.509%	$178.5951	$178.60	$178.60	$178.60
Purchase #6	$110.84	12.677%	$124.8912	$124.89	$124.90	$124.90
Purchase #7	$98.27	6.790%	$104.9425	$104.94	$104.95	$104.90
7 purchase totals =	$773.05		$851.1471	$851.15	$851.15	$851.00