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	$211.62	6.834%	$226.0821	$226.08	$226.10	$226.10
Purchase #2	$194.77	12.454%	$219.0267	$219.03	$219.05	$219.00
Purchase #3	$79.75	13.406%	$90.4413	$90.44	$90.45	$90.40
Purchase #4	$233.86	11.558%	$260.8895	$260.89	$260.90	$260.90
Purchase #5	$66.93	7.224%	$71.765	$71.77	$71.75	$71.80
Purchase #6	$137.78	6.466%	$146.6889	$146.69	$146.70	$146.70
Purchase #7	$73.30	7.580%	$78.8561	$78.86	$78.85	$78.90
7 purchase totals =	$998.01		$1,093.7496	$1,093.76	$1,093.80	$1,093.80