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	$31.31	7.102%	$33.5336	$33.53	$33.55	$33.50
Purchase #2	$96.98	10.715%	$107.3714	$107.37	$107.35	$107.40
Purchase #3	$43.80	4.147%	$45.6164	$45.62	$45.60	$45.60
Purchase #4	$36.84	13.647%	$41.8676	$41.87	$41.85	$41.90
Purchase #5	$212.66	4.714%	$222.6848	$222.68	$222.70	$222.70
Purchase #6	$77.48	6.823%	$82.7665	$82.77	$82.75	$82.80
Purchase #7	$50.50	5.272%	$53.1624	$53.16	$53.15	$53.20
7 purchase totals =	$549.57		$587.0027	$587.00	$586.95	$587.10