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	$71.39	7.667%	$76.8635	$76.86	$76.85	$76.90
Purchase #2	$202.34	7.811%	$218.1448	$218.14	$218.15	$218.10
Purchase #3	$214.42	11.127%	$238.2785	$238.28	$238.30	$238.30
Purchase #4	$138.98	8.507%	$150.803	$150.80	$150.80	$150.80
Purchase #5	$82.41	11.713%	$92.0627	$92.06	$92.05	$92.10
Purchase #6	$92.89	5.729%	$98.2117	$98.21	$98.20	$98.20
Purchase #7	$190.36	13.520%	$216.0967	$216.10	$216.10	$216.10
7 purchase totals =	$992.79		$1,090.4609	$1,090.45	$1,090.45	$1,090.50