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	$40.31	12.777%	$45.4604	$45.46	$45.45	$45.50
Purchase #2	$130.26	7.742%	$140.3447	$140.34	$140.35	$140.30
Purchase #3	$6.69	4.525%	$6.9927	$6.99	$7.00	$7.00
Purchase #4	$42.54	11.385%	$47.3832	$47.38	$47.40	$47.40
Purchase #5	$177.58	9.509%	$194.4661	$194.47	$194.45	$194.50
Purchase #6	$185.43	12.320%	$208.275	$208.28	$208.30	$208.30
Purchase #7	$52.37	9.842%	$57.5243	$57.52	$57.50	$57.50
7 purchase totals =	$635.18		$700.4464	$700.44	$700.45	$700.50