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	$198.45	12.524%	$223.3039	$223.30	$223.30	$223.30
Purchase #2	$225.47	12.774%	$254.2715	$254.27	$254.25	$254.30
Purchase #3	$112.99	4.623%	$118.2135	$118.21	$118.20	$118.20
Purchase #4	$214.57	12.751%	$241.9298	$241.93	$241.95	$241.90
Purchase #5	$82.47	12.228%	$92.5544	$92.55	$92.55	$92.60
Purchase #6	$119.62	10.857%	$132.6071	$132.61	$132.60	$132.60
Purchase #7	$72.89	8.230%	$78.8888	$78.89	$78.90	$78.90
7 purchase totals =	$1,026.46		$1,141.7690	$1,141.76	$1,141.75	$1,141.80