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	$210.99	5.693%	$223.0017	$223.00	$223.00	$223.00
Purchase #2	$165.98	7.577%	$178.5563	$178.56	$178.55	$178.60
Purchase #3	$62.51	7.528%	$67.2158	$67.22	$67.20	$67.20
Purchase #4	$98.86	12.827%	$111.5408	$111.54	$111.55	$111.50
Purchase #5	$126.96	8.600%	$137.8786	$137.88	$137.90	$137.90
Purchase #6	$40.35	8.271%	$43.6873	$43.69	$43.70	$43.70
Purchase #7	$210.86	11.220%	$234.5185	$234.52	$234.50	$234.50
7 purchase totals =	$916.51		$996.3990	$996.41	$996.40	$996.40