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	$143.77	8.172%	$155.5189	$155.52	$155.50	$155.50
Purchase #2	$63.85	13.248%	$72.3088	$72.31	$72.30	$72.30
Purchase #3	$132.71	13.208%	$150.2383	$150.24	$150.25	$150.20
Purchase #4	$123.86	8.114%	$133.91	$133.91	$133.90	$133.90
Purchase #5	$247.36	5.307%	$260.4874	$260.49	$260.50	$260.50
Purchase #6	$101.42	6.814%	$108.3308	$108.33	$108.35	$108.30
Purchase #7	$187.82	13.107%	$212.4376	$212.44	$212.45	$212.40
7 purchase totals =	$1,000.79		$1,093.2318	$1,093.24	$1,093.25	$1,093.10