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	$167.60	7.178%	$179.6303	$179.63	$179.65	$179.60
Purchase #2	$127.82	3.170%	$131.8719	$131.87	$131.85	$131.90
Purchase #3	$55.55	7.593%	$59.7679	$59.77	$59.75	$59.80
Purchase #4	$239.93	7.718%	$258.4478	$258.45	$258.45	$258.40
Purchase #5	$107.89	10.384%	$119.0933	$119.09	$119.10	$119.10
Purchase #6	$166.62	9.263%	$182.054	$182.05	$182.05	$182.10
Purchase #7	$20.60	7.579%	$22.1613	$22.16	$22.15	$22.20
7 purchase totals =	$886.01		$953.0265	$953.02	$953.00	$953.10