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	$115.85	10.320%	$127.8057	$127.81	$127.80	$127.80
Purchase #2	$79.37	7.585%	$85.3902	$85.39	$85.40	$85.40
Purchase #3	$175.46	7.366%	$188.3844	$188.38	$188.40	$188.40
Purchase #4	$94.92	5.159%	$99.8169	$99.82	$99.80	$99.80
Purchase #5	$33.60	4.372%	$35.069	$35.07	$35.05	$35.10
Purchase #6	$60.49	3.392%	$62.5418	$62.54	$62.55	$62.50
Purchase #7	$224.99	7.703%	$242.321	$242.32	$242.30	$242.30
7 purchase totals =	$784.68		$841.3290	$841.33	$841.30	$841.30