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	$81.51	7.397%	$87.5393	$87.54	$87.55	$87.50
Purchase #2	$241.26	9.695%	$264.6502	$264.65	$264.65	$264.70
Purchase #3	$210.69	4.137%	$219.4062	$219.41	$219.40	$219.40
Purchase #4	$193.37	3.792%	$200.7026	$200.70	$200.70	$200.70
Purchase #5	$74.40	5.418%	$78.431	$78.43	$78.45	$78.40
Purchase #6	$48.71	7.664%	$52.4431	$52.44	$52.45	$52.40
Purchase #7	$135.44	4.554%	$141.6079	$141.61	$141.60	$141.60
7 purchase totals =	$985.38		$1,044.7803	$1,044.78	$1,044.80	$1,044.70