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	$156.71	6.415%	$166.7629	$166.76	$166.75	$166.80
Purchase #2	$198.76	13.218%	$225.0321	$225.03	$225.05	$225.00
Purchase #3	$249.92	3.654%	$259.0521	$259.05	$259.05	$259.10
Purchase #4	$64.89	4.557%	$67.847	$67.85	$67.85	$67.80
Purchase #5	$213.25	13.204%	$241.4075	$241.41	$241.40	$241.40
Purchase #6	$71.32	10.158%	$78.5647	$78.56	$78.55	$78.60
Purchase #7	$180.31	3.185%	$186.0529	$186.05	$186.05	$186.10
7 purchase totals =	$1,135.16		$1,224.7192	$1,224.71	$1,224.70	$1,224.80