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	$176.83	7.431%	$189.9702	$189.97	$189.95	$190.00
Purchase #2	$67.62	4.820%	$70.8793	$70.88	$70.90	$70.90
Purchase #3	$148.40	10.763%	$164.3723	$164.37	$164.35	$164.40
Purchase #4	$212.89	10.193%	$234.5899	$234.59	$234.60	$234.60
Purchase #5	$188.94	4.140%	$196.7621	$196.76	$196.75	$196.80
Purchase #6	$50.78	9.643%	$55.6767	$55.68	$55.70	$55.70
Purchase #7	$212.83	12.185%	$238.7633	$238.76	$238.75	$238.80
7 purchase totals =	$1,058.29		$1,151.0138	$1,151.01	$1,151.00	$1,151.20