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	$152.78	9.477%	$167.259	$167.26	$167.25	$167.30
Purchase #2	$114.43	9.305%	$125.0777	$125.08	$125.10	$125.10
Purchase #3	$87.48	13.796%	$99.5487	$99.55	$99.55	$99.50
Purchase #4	$98.88	10.711%	$109.471	$109.47	$109.45	$109.50
Purchase #5	$111.43	6.743%	$118.9437	$118.94	$118.95	$118.90
Purchase #6	$95.96	10.265%	$105.8103	$105.81	$105.80	$105.80
Purchase #7	$115.55	6.842%	$123.4559	$123.46	$123.45	$123.50
7 purchase totals =	$776.51		$849.5663	$849.57	$849.55	$849.60