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	$184.67	3.366%	$190.886	$190.89	$190.90	$190.90
Purchase #2	$45.90	12.727%	$51.7417	$51.74	$51.75	$51.70
Purchase #3	$52.59	10.155%	$57.9305	$57.93	$57.95	$57.90
Purchase #4	$91.86	7.241%	$98.5116	$98.51	$98.50	$98.50
Purchase #5	$10.75	13.327%	$12.1827	$12.18	$12.20	$12.20
Purchase #6	$227.62	6.719%	$242.9138	$242.91	$242.90	$242.90
Purchase #7	$205.95	4.651%	$215.5287	$215.53	$215.55	$215.50
7 purchase totals =	$819.34		$869.6950	$869.69	$869.75	$869.60