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	$162.67	5.613%	$171.8007	$171.80	$171.80	$171.80
Purchase #2	$115.67	11.406%	$128.8633	$128.86	$128.85	$128.90
Purchase #3	$48.61	13.745%	$55.2914	$55.29	$55.30	$55.30
Purchase #4	$67.55	5.203%	$71.0646	$71.06	$71.05	$71.10
Purchase #5	$78.43	5.635%	$82.8495	$82.85	$82.85	$82.80
Purchase #6	$227.92	4.249%	$237.6043	$237.60	$237.60	$237.60
Purchase #7	$206.61	3.533%	$213.9095	$213.91	$213.90	$213.90
7 purchase totals =	$907.46		$961.3833	$961.37	$961.35	$961.40