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	$127.59	13.866%	$145.2816	$145.28	$145.30	$145.30
Purchase #2	$171.82	12.292%	$192.9401	$192.94	$192.95	$192.90
Purchase #3	$80.65	11.429%	$89.8675	$89.87	$89.85	$89.90
Purchase #4	$26.67	3.535%	$27.6128	$27.61	$27.60	$27.60
Purchase #5	$81.29	10.315%	$89.6751	$89.68	$89.70	$89.70
Purchase #6	$224.43	12.671%	$252.8675	$252.87	$252.85	$252.90
Purchase #7	$230.36	7.121%	$246.7639	$246.76	$246.75	$246.80
7 purchase totals =	$942.81		$1,045.0085	$1,045.01	$1,045.00	$1,045.10