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	$107.31	6.532%	$114.3195	$114.32	$114.30	$114.30
Purchase #2	$141.88	9.216%	$154.9557	$154.96	$154.95	$155.00
Purchase #3	$67.82	5.425%	$71.4992	$71.50	$71.50	$71.50
Purchase #4	$94.52	9.511%	$103.5098	$103.51	$103.50	$103.50
Purchase #5	$55.79	7.239%	$59.8286	$59.83	$59.85	$59.80
Purchase #6	$60.32	12.748%	$68.0096	$68.01	$68.00	$68.00
Purchase #7	$172.54	3.744%	$178.9999	$179.00	$179.00	$179.00
7 purchase totals =	$700.18		$751.1223	$751.13	$751.10	$751.10