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	$186.74	5.127%	$196.3142	$196.31	$196.30	$196.30
Purchase #2	$159.91	4.605%	$167.2739	$167.27	$167.25	$167.30
Purchase #3	$81.74	6.760%	$87.2656	$87.27	$87.25	$87.30
Purchase #4	$147.40	12.724%	$166.1552	$166.16	$166.15	$166.20
Purchase #5	$200.33	11.624%	$223.6164	$223.62	$223.60	$223.60
Purchase #6	$205.26	11.596%	$229.0619	$229.06	$229.05	$229.10
Purchase #7	$248.84	13.442%	$282.2891	$282.29	$282.30	$282.30
7 purchase totals =	$1,230.22		$1,351.9763	$1,351.98	$1,351.90	$1,352.10