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	$219.31	5.265%	$230.8567	$230.86	$230.85	$230.90
Purchase #2	$178.46	9.461%	$195.3441	$195.34	$195.35	$195.30
Purchase #3	$106.84	12.208%	$119.883	$119.88	$119.90	$119.90
Purchase #4	$117.40	8.423%	$127.2886	$127.29	$127.30	$127.30
Purchase #5	$141.37	9.365%	$154.6093	$154.61	$154.60	$154.60
Purchase #6	$211.81	7.495%	$227.6852	$227.69	$227.70	$227.70
Purchase #7	$40.32	11.270%	$44.8641	$44.86	$44.85	$44.90
7 purchase totals =	$1,015.51		$1,100.5310	$1,100.53	$1,100.55	$1,100.60