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	$42.89	6.493%	$45.6748	$45.67	$45.65	$45.70
Purchase #2	$150.90	4.443%	$157.6045	$157.60	$157.60	$157.60
Purchase #3	$194.77	8.787%	$211.8844	$211.88	$211.90	$211.90
Purchase #4	$104.45	12.252%	$117.2472	$117.25	$117.25	$117.20
Purchase #5	$91.71	8.297%	$99.3192	$99.32	$99.30	$99.30
Purchase #6	$57.63	5.312%	$60.6913	$60.69	$60.70	$60.70
Purchase #7	$46.30	9.805%	$50.8397	$50.84	$50.85	$50.80
7 purchase totals =	$688.65		$743.2611	$743.25	$743.25	$743.20