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	$41.52	4.702%	$43.4723	$43.47	$43.45	$43.50
Purchase #2	$137.53	9.551%	$150.6655	$150.67	$150.65	$150.70
Purchase #3	$169.70	4.776%	$177.8049	$177.80	$177.80	$177.80
Purchase #4	$80.66	10.578%	$89.1922	$89.19	$89.20	$89.20
Purchase #5	$18.80	8.459%	$20.3903	$20.39	$20.40	$20.40
Purchase #6	$147.88	10.169%	$162.9179	$162.92	$162.90	$162.90
Purchase #7	$137.36	3.202%	$141.7583	$141.76	$141.75	$141.80
7 purchase totals =	$733.45		$786.2014	$786.20	$786.15	$786.30