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	$185.94	4.418%	$194.1548	$194.15	$194.15	$194.20
Purchase #2	$48.50	12.508%	$54.5664	$54.57	$54.55	$54.60
Purchase #3	$99.89	4.509%	$104.394	$104.39	$104.40	$104.40
Purchase #4	$205.47	4.119%	$213.9333	$213.93	$213.95	$213.90
Purchase #5	$156.53	5.349%	$164.9028	$164.90	$164.90	$164.90
Purchase #6	$83.36	8.309%	$90.2864	$90.29	$90.30	$90.30
Purchase #7	$129.41	7.190%	$138.7146	$138.71	$138.70	$138.70
7 purchase totals =	$909.10		$960.9523	$960.94	$960.95	$961.00