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	$50.27	5.360%	$52.9645	$52.96	$52.95	$53.00
Purchase #2	$200.31	13.346%	$227.0434	$227.04	$227.05	$227.00
Purchase #3	$86.40	3.652%	$89.5553	$89.56	$89.55	$89.60
Purchase #4	$119.92	9.642%	$131.4827	$131.48	$131.50	$131.50
Purchase #5	$108.75	10.770%	$120.4624	$120.46	$120.45	$120.50
Purchase #6	$68.55	8.795%	$74.579	$74.58	$74.60	$74.60
Purchase #7	$68.65	3.556%	$71.0912	$71.09	$71.10	$71.10
7 purchase totals =	$702.85		$767.1785	$767.17	$767.20	$767.30