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	$212.85	4.437%	$222.2942	$222.29	$222.30	$222.30
Purchase #2	$115.96	13.591%	$131.7201	$131.72	$131.70	$131.70
Purchase #3	$43.98	5.760%	$46.5132	$46.51	$46.50	$46.50
Purchase #4	$194.55	8.831%	$211.7307	$211.73	$211.75	$211.70
Purchase #5	$80.99	10.686%	$89.6446	$89.64	$89.65	$89.60
Purchase #6	$105.78	6.841%	$113.0164	$113.02	$113.00	$113.00
Purchase #7	$173.84	5.279%	$183.017	$183.02	$183.00	$183.00
7 purchase totals =	$927.95		$997.9362	$997.93	$997.90	$997.80