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	$237.59	13.382%	$269.3843	$269.38	$269.40	$269.40
Purchase #2	$29.42	8.383%	$31.8863	$31.89	$31.90	$31.90
Purchase #3	$195.25	3.607%	$202.2927	$202.29	$202.30	$202.30
Purchase #4	$78.35	12.538%	$88.1735	$88.17	$88.15	$88.20
Purchase #5	$36.25	4.415%	$37.8504	$37.85	$37.85	$37.90
Purchase #6	$17.83	13.291%	$20.1998	$20.20	$20.20	$20.20
Purchase #7	$52.98	12.791%	$59.7567	$59.76	$59.75	$59.80
7 purchase totals =	$647.67		$709.5437	$709.54	$709.55	$709.70