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	$122.65	4.309%	$127.935	$127.94	$127.95	$127.90
Purchase #2	$200.89	7.725%	$216.4088	$216.41	$216.40	$216.40
Purchase #3	$102.72	4.775%	$107.6249	$107.62	$107.60	$107.60
Purchase #4	$115.78	10.553%	$127.9983	$128.00	$128.00	$128.00
Purchase #5	$127.88	11.374%	$142.4251	$142.43	$142.45	$142.40
Purchase #6	$227.74	3.342%	$235.3511	$235.35	$235.35	$235.40
Purchase #7	$212.54	4.797%	$222.7355	$222.74	$222.75	$222.70
7 purchase totals =	$1,110.20		$1,180.4787	$1,180.49	$1,180.50	$1,180.40