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	$183.77	11.557%	$205.0083	$205.01	$205.00	$205.00
Purchase #2	$49.72	9.435%	$54.4111	$54.41	$54.40	$54.40
Purchase #3	$26.34	11.501%	$29.3694	$29.37	$29.35	$29.40
Purchase #4	$177.48	13.218%	$200.9393	$200.94	$200.95	$200.90
Purchase #5	$56.94	3.820%	$59.1151	$59.12	$59.10	$59.10
Purchase #6	$204.77	5.737%	$216.5177	$216.52	$216.50	$216.50
Purchase #7	$169.40	3.352%	$175.0783	$175.08	$175.10	$175.10
7 purchase totals =	$868.42		$940.4392	$940.45	$940.40	$940.40