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	$169.25	7.251%	$181.5223	$181.52	$181.50	$181.50
Purchase #2	$179.64	8.264%	$194.4854	$194.49	$194.50	$194.50
Purchase #3	$177.34	4.354%	$185.0614	$185.06	$185.05	$185.10
Purchase #4	$91.62	12.577%	$103.143	$103.14	$103.15	$103.10
Purchase #5	$91.25	9.580%	$99.9918	$99.99	$100.00	$100.00
Purchase #6	$235.74	12.621%	$265.4927	$265.49	$265.50	$265.50
Purchase #7	$205.35	6.606%	$218.9154	$218.92	$218.90	$218.90
7 purchase totals =	$1,150.19		$1,248.6120	$1,248.61	$1,248.60	$1,248.60