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	$210.83	13.212%	$238.6849	$238.68	$238.70	$238.70
Purchase #2	$57.60	7.467%	$61.901	$61.90	$61.90	$61.90
Purchase #3	$169.30	5.777%	$179.0805	$179.08	$179.10	$179.10
Purchase #4	$89.89	9.822%	$98.719	$98.72	$98.70	$98.70
Purchase #5	$38.77	9.180%	$42.3291	$42.33	$42.35	$42.30
Purchase #6	$13.78	3.823%	$14.3068	$14.31	$14.30	$14.30
Purchase #7	$50.84	12.621%	$57.2565	$57.26	$57.25	$57.30
7 purchase totals =	$631.01		$692.2778	$692.28	$692.30	$692.30