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	$104.40	4.753%	$109.3621	$109.36	$109.35	$109.40
Purchase #2	$77.81	13.374%	$88.2163	$88.22	$88.20	$88.20
Purchase #3	$189.32	11.110%	$210.3535	$210.35	$210.35	$210.40
Purchase #4	$64.92	9.461%	$71.0621	$71.06	$71.05	$71.10
Purchase #5	$48.29	8.454%	$52.3724	$52.37	$52.35	$52.40
Purchase #6	$186.71	5.358%	$196.7139	$196.71	$196.70	$196.70
Purchase #7	$19.45	11.596%	$21.7054	$21.71	$21.70	$21.70
7 purchase totals =	$690.90		$749.7857	$749.78	$749.70	$749.90