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	$67.90	4.538%	$70.9813	$70.98	$71.00	$71.00
Purchase #2	$234.70	3.379%	$242.6305	$242.63	$242.65	$242.60
Purchase #3	$24.34	4.181%	$25.3577	$25.36	$25.35	$25.40
Purchase #4	$150.41	12.329%	$168.954	$168.95	$168.95	$169.00
Purchase #5	$128.28	8.780%	$139.543	$139.54	$139.55	$139.50
Purchase #6	$132.25	7.169%	$141.731	$141.73	$141.75	$141.70
Purchase #7	$178.83	7.536%	$192.3066	$192.31	$192.30	$192.30
7 purchase totals =	$916.71		$981.5041	$981.50	$981.55	$981.50