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	$101.48	8.623%	$110.2306	$110.23	$110.25	$110.20
Purchase #2	$106.85	11.799%	$119.4572	$119.46	$119.45	$119.50
Purchase #3	$40.32	10.575%	$44.5838	$44.58	$44.60	$44.60
Purchase #4	$250.73	8.248%	$271.4102	$271.41	$271.40	$271.40
Purchase #5	$123.72	7.804%	$133.3751	$133.38	$133.40	$133.40
Purchase #6	$145.90	12.851%	$164.6496	$164.65	$164.65	$164.60
Purchase #7	$250.80	11.578%	$279.8376	$279.84	$279.85	$279.80
7 purchase totals =	$1,019.80		$1,123.5441	$1,123.55	$1,123.60	$1,123.50