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	$73.32	4.173%	$76.3796	$76.38	$76.40	$76.40
Purchase #2	$71.64	9.516%	$78.4573	$78.46	$78.45	$78.50
Purchase #3	$197.84	11.479%	$220.5501	$220.55	$220.55	$220.60
Purchase #4	$187.80	6.297%	$199.6258	$199.63	$199.65	$199.60
Purchase #5	$143.31	11.742%	$160.1375	$160.14	$160.15	$160.10
Purchase #6	$86.46	3.548%	$89.5276	$89.53	$89.55	$89.50
Purchase #7	$160.63	11.430%	$178.99	$178.99	$179.00	$179.00
7 purchase totals =	$921.00		$1,003.6679	$1,003.68	$1,003.75	$1,003.70