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	$118.43	7.597%	$127.4271	$127.43	$127.45	$127.40
Purchase #2	$32.46	13.788%	$36.9356	$36.94	$36.95	$36.90
Purchase #3	$242.82	4.361%	$253.4094	$253.41	$253.40	$253.40
Purchase #4	$60.36	11.790%	$67.4764	$67.48	$67.50	$67.50
Purchase #5	$116.88	13.177%	$132.2813	$132.28	$132.30	$132.30
Purchase #6	$28.59	10.517%	$31.5968	$31.60	$31.60	$31.60
Purchase #7	$58.76	6.255%	$62.4354	$62.44	$62.45	$62.40
7 purchase totals =	$658.30		$711.5620	$711.58	$711.65	$711.50