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	$203.46	11.598%	$227.0573	$227.06	$227.05	$227.10
Purchase #2	$232.99	3.203%	$240.4527	$240.45	$240.45	$240.50
Purchase #3	$59.30	13.536%	$67.3268	$67.33	$67.35	$67.30
Purchase #4	$196.30	13.548%	$222.8947	$222.89	$222.90	$222.90
Purchase #5	$108.86	9.723%	$119.4445	$119.44	$119.45	$119.40
Purchase #6	$97.86	4.524%	$102.2872	$102.29	$102.30	$102.30
Purchase #7	$50.98	9.769%	$55.9602	$55.96	$55.95	$56.00
7 purchase totals =	$949.75		$1,035.4234	$1,035.42	$1,035.45	$1,035.50