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	$162.70	3.354%	$168.157	$168.16	$168.15	$168.20
Purchase #2	$13.95	8.296%	$15.1073	$15.11	$15.10	$15.10
Purchase #3	$135.57	4.347%	$141.4632	$141.46	$141.45	$141.50
Purchase #4	$102.28	6.143%	$108.5631	$108.56	$108.55	$108.60
Purchase #5	$28.67	4.320%	$29.9085	$29.91	$29.90	$29.90
Purchase #6	$160.38	9.389%	$175.4381	$175.44	$175.45	$175.40
Purchase #7	$56.39	5.609%	$59.5529	$59.55	$59.55	$59.60
7 purchase totals =	$659.94		$698.1901	$698.19	$698.15	$698.30