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	$12.58	7.620%	$13.5386	$13.54	$13.55	$13.50
Purchase #2	$89.56	10.385%	$98.8608	$98.86	$98.85	$98.90
Purchase #3	$7.26	4.288%	$7.5713	$7.57	$7.55	$7.60
Purchase #4	$151.94	3.535%	$157.3111	$157.31	$157.30	$157.30
Purchase #5	$211.89	5.161%	$222.8256	$222.83	$222.85	$222.80
Purchase #6	$92.28	10.662%	$102.1189	$102.12	$102.10	$102.10
Purchase #7	$159.59	3.385%	$164.9921	$164.99	$165.00	$165.00
7 purchase totals =	$725.10		$767.2184	$767.22	$767.20	$767.20