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	$121.78	4.225%	$126.9252	$126.93	$126.95	$126.90
Purchase #2	$57.38	12.206%	$64.3838	$64.38	$64.40	$64.40
Purchase #3	$96.98	9.750%	$106.4356	$106.44	$106.45	$106.40
Purchase #4	$109.45	4.496%	$114.3709	$114.37	$114.35	$114.40
Purchase #5	$123.36	4.170%	$128.5041	$128.50	$128.50	$128.50
Purchase #6	$150.46	11.580%	$167.8833	$167.88	$167.90	$167.90
Purchase #7	$49.32	10.520%	$54.5085	$54.51	$54.50	$54.50
7 purchase totals =	$708.73		$763.0114	$763.01	$763.05	$763.00