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	$145.68	6.417%	$155.0283	$155.03	$155.05	$155.00
Purchase #2	$196.29	13.516%	$222.8206	$222.82	$222.80	$222.80
Purchase #3	$194.54	6.621%	$207.4205	$207.42	$207.40	$207.40
Purchase #4	$191.63	12.870%	$216.2928	$216.29	$216.30	$216.30
Purchase #5	$52.61	12.850%	$59.3704	$59.37	$59.35	$59.40
Purchase #6	$37.43	3.174%	$38.618	$38.62	$38.60	$38.60
Purchase #7	$198.86	12.646%	$224.0078	$224.01	$224.00	$224.00
7 purchase totals =	$1,017.04		$1,123.5584	$1,123.56	$1,123.50	$1,123.50