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	$87.92	7.140%	$94.1975	$94.20	$94.20	$94.20
Purchase #2	$73.44	6.369%	$78.1174	$78.12	$78.10	$78.10
Purchase #3	$49.54	12.543%	$55.7538	$55.75	$55.75	$55.80
Purchase #4	$142.95	11.131%	$158.8618	$158.86	$158.85	$158.90
Purchase #5	$100.28	4.636%	$104.929	$104.93	$104.95	$104.90
Purchase #6	$103.48	10.646%	$114.4965	$114.50	$114.50	$114.50
Purchase #7	$53.83	8.356%	$58.328	$58.33	$58.35	$58.30
7 purchase totals =	$611.44		$664.6840	$664.69	$664.70	$664.70