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	$40.74	12.801%	$45.9551	$45.96	$45.95	$46.00
Purchase #2	$83.79	6.315%	$89.0813	$89.08	$89.10	$89.10
Purchase #3	$178.85	3.746%	$185.5497	$185.55	$185.55	$185.50
Purchase #4	$126.71	10.510%	$140.0272	$140.03	$140.05	$140.00
Purchase #5	$37.78	9.411%	$41.3355	$41.34	$41.35	$41.30
Purchase #6	$11.87	7.102%	$12.713	$12.71	$12.70	$12.70
Purchase #7	$226.98	12.312%	$254.9258	$254.93	$254.95	$254.90
7 purchase totals =	$706.72		$769.5876	$769.60	$769.65	$769.50