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	$89.39	13.656%	$101.5971	$101.60	$101.60	$101.60
Purchase #2	$160.65	5.625%	$169.6866	$169.69	$169.70	$169.70
Purchase #3	$20.53	4.492%	$21.4522	$21.45	$21.45	$21.50
Purchase #4	$103.58	12.791%	$116.8289	$116.83	$116.85	$116.80
Purchase #5	$119.92	12.118%	$134.4519	$134.45	$134.45	$134.50
Purchase #6	$158.64	3.654%	$164.4367	$164.44	$164.45	$164.40
Purchase #7	$201.90	10.644%	$223.3902	$223.39	$223.40	$223.40
7 purchase totals =	$854.61		$931.8436	$931.85	$931.90	$931.90