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	$93.25	5.563%	$98.4375	$98.44	$98.45	$98.40
Purchase #2	$74.83	5.414%	$78.8813	$78.88	$78.90	$78.90
Purchase #3	$147.36	6.321%	$156.6746	$156.67	$156.65	$156.70
Purchase #4	$177.28	9.124%	$193.455	$193.46	$193.45	$193.50
Purchase #5	$98.86	12.524%	$111.2412	$111.24	$111.25	$111.20
Purchase #6	$140.79	13.127%	$159.2715	$159.27	$159.25	$159.30
Purchase #7	$105.31	10.775%	$116.6572	$116.66	$116.65	$116.70
7 purchase totals =	$837.68		$914.6183	$914.62	$914.60	$914.70