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	$247.86	10.780%	$274.5793	$274.58	$274.60	$274.60
Purchase #2	$177.50	10.525%	$196.1819	$196.18	$196.20	$196.20
Purchase #3	$64.99	4.496%	$67.912	$67.91	$67.90	$67.90
Purchase #4	$138.83	9.819%	$152.4617	$152.46	$152.45	$152.50
Purchase #5	$114.51	3.835%	$118.9015	$118.90	$118.90	$118.90
Purchase #6	$135.52	6.120%	$143.8138	$143.81	$143.80	$143.80
Purchase #7	$69.34	3.149%	$71.5235	$71.52	$71.50	$71.50
7 purchase totals =	$948.55		$1,025.3737	$1,025.36	$1,025.35	$1,025.40