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	$95.89	10.314%	$105.7801	$105.78	$105.80	$105.80
Purchase #2	$70.46	13.382%	$79.889	$79.89	$79.90	$79.90
Purchase #3	$53.95	12.170%	$60.5157	$60.52	$60.50	$60.50
Purchase #4	$11.88	12.472%	$13.3617	$13.36	$13.35	$13.40
Purchase #5	$71.25	9.495%	$78.0152	$78.02	$78.00	$78.00
Purchase #6	$92.90	6.388%	$98.8345	$98.83	$98.85	$98.80
Purchase #7	$233.34	12.787%	$263.1772	$263.18	$263.20	$263.20
7 purchase totals =	$629.67		$699.5734	$699.58	$699.60	$699.60