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	$139.86	9.623%	$153.3187	$153.32	$153.30	$153.30
Purchase #2	$173.32	13.113%	$196.0475	$196.05	$196.05	$196.00
Purchase #3	$123.43	4.476%	$128.9547	$128.95	$128.95	$129.00
Purchase #4	$20.48	3.839%	$21.2662	$21.27	$21.25	$21.30
Purchase #5	$20.52	13.331%	$23.2555	$23.26	$23.25	$23.30
Purchase #6	$213.95	9.266%	$233.7746	$233.77	$233.75	$233.80
Purchase #7	$12.95	9.802%	$14.2194	$14.22	$14.20	$14.20
7 purchase totals =	$704.51		$770.8366	$770.84	$770.75	$770.90