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	$233.38	11.166%	$259.4392	$259.44	$259.45	$259.40
Purchase #2	$145.76	4.663%	$152.5568	$152.56	$152.55	$152.60
Purchase #3	$150.81	12.182%	$169.1817	$169.18	$169.20	$169.20
Purchase #4	$78.59	13.160%	$88.9324	$88.93	$88.95	$88.90
Purchase #5	$98.82	4.272%	$103.0416	$103.04	$103.05	$103.00
Purchase #6	$143.92	12.718%	$162.2237	$162.22	$162.20	$162.20
Purchase #7	$184.37	11.367%	$205.3273	$205.33	$205.35	$205.30
7 purchase totals =	$1,035.65		$1,140.7027	$1,140.70	$1,140.75	$1,140.60