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	$167.74	12.752%	$189.1302	$189.13	$189.15	$189.10
Purchase #2	$95.55	7.143%	$102.3751	$102.38	$102.40	$102.40
Purchase #3	$112.61	3.149%	$116.1561	$116.16	$116.15	$116.20
Purchase #4	$54.26	9.823%	$59.59	$59.59	$59.60	$59.60
Purchase #5	$132.38	11.220%	$147.233	$147.23	$147.25	$147.20
Purchase #6	$64.43	3.113%	$66.4357	$66.44	$66.45	$66.40
Purchase #7	$59.96	11.659%	$66.9507	$66.95	$66.95	$67.00
7 purchase totals =	$686.93		$747.8708	$747.88	$747.95	$747.90