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	$97.43	4.583%	$101.8952	$101.90	$101.90	$101.90
Purchase #2	$183.85	4.150%	$191.4798	$191.48	$191.50	$191.50
Purchase #3	$213.85	4.617%	$223.7235	$223.72	$223.70	$223.70
Purchase #4	$111.61	5.858%	$118.1481	$118.15	$118.15	$118.10
Purchase #5	$51.72	8.839%	$56.2915	$56.29	$56.30	$56.30
Purchase #6	$186.75	4.389%	$194.9465	$194.95	$194.95	$194.90
Purchase #7	$226.36	8.126%	$244.754	$244.75	$244.75	$244.80
7 purchase totals =	$1,071.57		$1,131.2386	$1,131.24	$1,131.25	$1,131.20