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	$198.93	13.123%	$225.0356	$225.04	$225.05	$225.00
Purchase #2	$226.83	10.206%	$249.9803	$249.98	$250.00	$250.00
Purchase #3	$148.95	5.131%	$156.5926	$156.59	$156.60	$156.60
Purchase #4	$67.84	5.442%	$71.5319	$71.53	$71.55	$71.50
Purchase #5	$86.92	10.483%	$96.0318	$96.03	$96.05	$96.00
Purchase #6	$151.78	10.643%	$167.9339	$167.93	$167.95	$167.90
Purchase #7	$156.95	11.197%	$174.5237	$174.52	$174.50	$174.50
7 purchase totals =	$1,038.20		$1,141.6298	$1,141.62	$1,141.70	$1,141.50