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	$148.37	4.418%	$154.925	$154.93	$154.95	$154.90
Purchase #2	$125.35	11.111%	$139.2776	$139.28	$139.30	$139.30
Purchase #3	$17.54	6.795%	$18.7318	$18.73	$18.75	$18.70
Purchase #4	$85.76	4.568%	$89.6775	$89.68	$89.70	$89.70
Purchase #5	$38.57	10.141%	$42.4814	$42.48	$42.50	$42.50
Purchase #6	$56.57	5.601%	$59.7385	$59.74	$59.75	$59.70
Purchase #7	$189.82	8.489%	$205.9338	$205.93	$205.95	$205.90
7 purchase totals =	$661.98		$710.7656	$710.77	$710.90	$710.70