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	$61.99	8.698%	$67.3819	$67.38	$67.40	$67.40
Purchase #2	$66.51	3.862%	$69.0786	$69.08	$69.10	$69.10
Purchase #3	$114.74	7.865%	$123.7643	$123.76	$123.75	$123.80
Purchase #4	$57.31	3.801%	$59.4884	$59.49	$59.50	$59.50
Purchase #5	$226.88	4.233%	$236.4838	$236.48	$236.50	$236.50
Purchase #6	$94.90	12.235%	$106.511	$106.51	$106.50	$106.50
Purchase #7	$127.31	8.525%	$138.1632	$138.16	$138.15	$138.20
7 purchase totals =	$749.64		$800.8712	$800.86	$800.90	$801.00