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	$36.56	3.209%	$37.7332	$37.73	$37.75	$37.70
Purchase #2	$193.68	3.467%	$200.3949	$200.39	$200.40	$200.40
Purchase #3	$115.37	10.667%	$127.6765	$127.68	$127.70	$127.70
Purchase #4	$211.40	5.151%	$222.2892	$222.29	$222.30	$222.30
Purchase #5	$210.34	10.514%	$232.4551	$232.46	$232.45	$232.50
Purchase #6	$9.52	13.183%	$10.775	$10.78	$10.80	$10.80
Purchase #7	$32.44	3.795%	$33.6711	$33.67	$33.65	$33.70
7 purchase totals =	$809.31		$864.9950	$865.00	$865.05	$865.10