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	$113.88	12.663%	$128.3006	$128.30	$128.30	$128.30
Purchase #2	$10.33	4.146%	$10.7583	$10.76	$10.75	$10.80
Purchase #3	$102.50	11.697%	$114.4894	$114.49	$114.50	$114.50
Purchase #4	$38.55	10.355%	$42.5419	$42.54	$42.55	$42.50
Purchase #5	$165.49	12.854%	$186.7621	$186.76	$186.75	$186.80
Purchase #6	$51.34	9.718%	$56.3292	$56.33	$56.35	$56.30
Purchase #7	$230.90	3.175%	$238.2311	$238.23	$238.25	$238.20
7 purchase totals =	$712.99		$777.4126	$777.41	$777.45	$777.40