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	$133.41	6.752%	$142.4178	$142.42	$142.40	$142.40
Purchase #2	$61.79	10.103%	$68.0326	$68.03	$68.05	$68.00
Purchase #3	$87.32	12.863%	$98.552	$98.55	$98.55	$98.60
Purchase #4	$89.50	7.310%	$96.0425	$96.04	$96.05	$96.00
Purchase #5	$36.67	4.103%	$38.1746	$38.17	$38.15	$38.20
Purchase #6	$238.51	9.561%	$261.3139	$261.31	$261.30	$261.30
Purchase #7	$7.62	3.634%	$7.8969	$7.90	$7.90	$7.90
7 purchase totals =	$654.82		$712.4303	$712.42	$712.40	$712.40