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	$229.85	9.608%	$251.934	$251.93	$251.95	$251.90
Purchase #2	$141.85	6.293%	$150.7766	$150.78	$150.80	$150.80
Purchase #3	$144.29	13.792%	$164.1905	$164.19	$164.20	$164.20
Purchase #4	$173.91	9.769%	$190.8993	$190.90	$190.90	$190.90
Purchase #5	$147.59	7.179%	$158.1855	$158.19	$158.20	$158.20
Purchase #6	$5.31	4.859%	$5.568	$5.57	$5.55	$5.60
Purchase #7	$134.77	3.444%	$139.4115	$139.41	$139.40	$139.40
7 purchase totals =	$977.57		$1,060.9654	$1,060.97	$1,061.00	$1,061.00