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	$63.31	3.280%	$65.3866	$65.39	$65.40	$65.40
Purchase #2	$57.29	12.287%	$64.3292	$64.33	$64.35	$64.30
Purchase #3	$42.53	7.247%	$45.6121	$45.61	$45.60	$45.60
Purchase #4	$243.62	7.402%	$261.6528	$261.65	$261.65	$261.70
Purchase #5	$141.74	5.487%	$149.5173	$149.52	$149.50	$149.50
Purchase #6	$19.82	5.340%	$20.8784	$20.88	$20.90	$20.90
Purchase #7	$102.59	4.795%	$107.5092	$107.51	$107.50	$107.50
7 purchase totals =	$670.90		$714.8856	$714.89	$714.90	$714.90