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	$114.44	7.798%	$123.364	$123.36	$123.35	$123.40
Purchase #2	$214.87	7.260%	$230.4696	$230.47	$230.45	$230.50
Purchase #3	$144.85	13.468%	$164.3584	$164.36	$164.35	$164.40
Purchase #4	$145.76	12.709%	$164.2846	$164.28	$164.30	$164.30
Purchase #5	$131.72	7.803%	$141.9981	$142.00	$142.00	$142.00
Purchase #6	$70.74	6.755%	$75.5185	$75.52	$75.50	$75.50
Purchase #7	$202.66	12.666%	$228.3289	$228.33	$228.35	$228.30
7 purchase totals =	$1,025.04		$1,128.3221	$1,128.32	$1,128.30	$1,128.40