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	$140.44	9.375%	$153.6063	$153.61	$153.60	$153.60
Purchase #2	$63.70	12.679%	$71.7765	$71.78	$71.80	$71.80
Purchase #3	$192.98	8.443%	$209.2733	$209.27	$209.25	$209.30
Purchase #4	$63.83	5.158%	$67.1224	$67.12	$67.10	$67.10
Purchase #5	$91.60	6.302%	$97.3726	$97.37	$97.35	$97.40
Purchase #6	$98.45	9.162%	$107.47	$107.47	$107.45	$107.50
Purchase #7	$84.43	5.529%	$89.0981	$89.10	$89.10	$89.10
7 purchase totals =	$735.43		$795.7192	$795.72	$795.65	$795.80