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	$214.75	13.872%	$244.5401	$244.54	$244.55	$244.50
Purchase #2	$35.77	9.136%	$39.0379	$39.04	$39.05	$39.00
Purchase #3	$29.46	12.415%	$33.1175	$33.12	$33.10	$33.10
Purchase #4	$242.61	4.288%	$253.0131	$253.01	$253.00	$253.00
Purchase #5	$159.25	5.675%	$168.2874	$168.29	$168.30	$168.30
Purchase #6	$126.25	11.820%	$141.1728	$141.17	$141.15	$141.20
Purchase #7	$113.34	4.470%	$118.4063	$118.41	$118.40	$118.40
7 purchase totals =	$921.43		$997.5751	$997.58	$997.55	$997.50