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	$49.62	11.477%	$55.3149	$55.31	$55.30	$55.30
Purchase #2	$109.93	3.726%	$114.026	$114.03	$114.05	$114.00
Purchase #3	$201.50	4.231%	$210.0255	$210.03	$210.05	$210.00
Purchase #4	$96.56	6.203%	$102.5496	$102.55	$102.55	$102.50
Purchase #5	$109.79	4.124%	$114.3177	$114.32	$114.30	$114.30
Purchase #6	$101.59	13.780%	$115.5891	$115.59	$115.60	$115.60
Purchase #7	$86.37	5.223%	$90.8811	$90.88	$90.90	$90.90
7 purchase totals =	$755.36		$802.7039	$802.71	$802.75	$802.60