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	$202.27	12.566%	$227.6872	$227.69	$227.70	$227.70
Purchase #2	$211.47	8.735%	$229.9419	$229.94	$229.95	$229.90
Purchase #3	$114.97	11.367%	$128.0386	$128.04	$128.05	$128.00
Purchase #4	$101.55	12.200%	$113.9391	$113.94	$113.95	$113.90
Purchase #5	$170.72	13.686%	$194.0847	$194.08	$194.10	$194.10
Purchase #6	$65.42	11.156%	$72.7183	$72.72	$72.70	$72.70
Purchase #7	$99.69	9.802%	$109.4616	$109.46	$109.45	$109.50
7 purchase totals =	$966.09		$1,075.8714	$1,075.87	$1,075.90	$1,075.80