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	$30.86	4.133%	$32.1354	$32.14	$32.15	$32.10
Purchase #2	$241.55	7.868%	$260.5552	$260.56	$260.55	$260.60
Purchase #3	$152.66	6.599%	$162.734	$162.73	$162.75	$162.70
Purchase #4	$63.93	13.232%	$72.3892	$72.39	$72.40	$72.40
Purchase #5	$238.32	6.846%	$254.6354	$254.64	$254.65	$254.60
Purchase #6	$114.77	10.704%	$127.055	$127.06	$127.05	$127.10
Purchase #7	$178.32	13.717%	$202.7802	$202.78	$202.80	$202.80
7 purchase totals =	$1,020.41		$1,112.2844	$1,112.30	$1,112.35	$1,112.30