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	$42.60	9.618%	$46.6973	$46.70	$46.70	$46.70
Purchase #2	$185.26	13.480%	$210.233	$210.23	$210.25	$210.20
Purchase #3	$120.72	9.808%	$132.5602	$132.56	$132.55	$132.60
Purchase #4	$34.45	7.611%	$37.072	$37.07	$37.05	$37.10
Purchase #5	$132.97	3.489%	$137.6093	$137.61	$137.60	$137.60
Purchase #6	$91.86	13.326%	$104.1013	$104.10	$104.10	$104.10
Purchase #7	$163.46	13.543%	$185.5974	$185.60	$185.60	$185.60
7 purchase totals =	$771.32		$853.8705	$853.87	$853.85	$853.90