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	$178.63	6.562%	$190.3517	$190.35	$190.35	$190.40
Purchase #2	$137.45	10.584%	$151.9977	$152.00	$152.00	$152.00
Purchase #3	$61.46	9.575%	$67.3448	$67.34	$67.35	$67.30
Purchase #4	$34.37	6.124%	$36.4748	$36.47	$36.45	$36.50
Purchase #5	$95.89	3.672%	$99.4111	$99.41	$99.40	$99.40
Purchase #6	$97.58	6.666%	$104.0847	$104.08	$104.10	$104.10
Purchase #7	$103.30	4.374%	$107.8183	$107.82	$107.80	$107.80
7 purchase totals =	$708.68		$757.4831	$757.47	$757.45	$757.50