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	$202.26	3.532%	$209.4038	$209.40	$209.40	$209.40
Purchase #2	$141.45	12.201%	$158.7083	$158.71	$158.70	$158.70
Purchase #3	$38.69	12.190%	$43.4063	$43.41	$43.40	$43.40
Purchase #4	$97.62	9.834%	$107.22	$107.22	$107.20	$107.20
Purchase #5	$163.65	13.581%	$185.8753	$185.88	$185.90	$185.90
Purchase #6	$113.91	11.627%	$127.1543	$127.15	$127.15	$127.20
Purchase #7	$164.73	10.817%	$182.5488	$182.55	$182.55	$182.50
7 purchase totals =	$922.31		$1,014.3168	$1,014.32	$1,014.30	$1,014.30