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	$45.89	4.870%	$48.1248	$48.12	$48.10	$48.10
Purchase #2	$206.81	9.242%	$225.9234	$225.92	$225.90	$225.90
Purchase #3	$239.77	3.466%	$248.0804	$248.08	$248.10	$248.10
Purchase #4	$88.84	13.174%	$100.5438	$100.54	$100.55	$100.50
Purchase #5	$181.81	4.872%	$190.6678	$190.67	$190.65	$190.70
Purchase #6	$35.78	10.545%	$39.553	$39.55	$39.55	$39.60
Purchase #7	$225.34	5.272%	$237.2199	$237.22	$237.20	$237.20
7 purchase totals =	$1,024.24		$1,090.1131	$1,090.10	$1,090.05	$1,090.10