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	$96.82	4.548%	$101.2234	$101.22	$101.20	$101.20
Purchase #2	$216.68	9.872%	$238.0706	$238.07	$238.05	$238.10
Purchase #3	$70.28	10.429%	$77.6095	$77.61	$77.60	$77.60
Purchase #4	$163.52	6.700%	$174.4758	$174.48	$174.50	$174.50
Purchase #5	$42.81	4.192%	$44.6046	$44.60	$44.60	$44.60
Purchase #6	$131.90	4.550%	$137.9015	$137.90	$137.90	$137.90
Purchase #7	$172.39	6.450%	$183.5092	$183.51	$183.50	$183.50
7 purchase totals =	$894.40		$957.3946	$957.39	$957.35	$957.40