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	$243.47	11.680%	$271.9073	$271.91	$271.90	$271.90
Purchase #2	$215.77	6.353%	$229.4779	$229.48	$229.50	$229.50
Purchase #3	$97.41	4.789%	$102.075	$102.08	$102.10	$102.10
Purchase #4	$150.86	13.261%	$170.8655	$170.87	$170.85	$170.90
Purchase #5	$58.86	7.559%	$63.3092	$63.31	$63.30	$63.30
Purchase #6	$158.65	12.629%	$178.6859	$178.69	$178.70	$178.70
Purchase #7	$31.58	3.769%	$32.7703	$32.77	$32.75	$32.80
7 purchase totals =	$956.60		$1,049.0911	$1,049.11	$1,049.10	$1,049.20