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	$30.60	9.681%	$33.5624	$33.56	$33.55	$33.60
Purchase #2	$109.84	12.325%	$123.3778	$123.38	$123.40	$123.40
Purchase #3	$248.28	4.511%	$259.4799	$259.48	$259.50	$259.50
Purchase #4	$158.37	9.410%	$173.2726	$173.27	$173.25	$173.30
Purchase #5	$117.32	4.104%	$122.1348	$122.13	$122.15	$122.10
Purchase #6	$238.36	11.235%	$265.1397	$265.14	$265.15	$265.10
Purchase #7	$248.74	3.177%	$256.6425	$256.64	$256.65	$256.60
7 purchase totals =	$1,151.51		$1,233.6097	$1,233.60	$1,233.65	$1,233.60