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	$163.94	6.524%	$174.6354	$174.64	$174.65	$174.60
Purchase #2	$119.89	13.300%	$135.8354	$135.84	$135.85	$135.80
Purchase #3	$45.98	11.804%	$51.4075	$51.41	$51.40	$51.40
Purchase #4	$110.83	11.499%	$123.5743	$123.57	$123.55	$123.60
Purchase #5	$167.86	7.738%	$180.849	$180.85	$180.85	$180.80
Purchase #6	$6.97	12.387%	$7.8334	$7.83	$7.85	$7.80
Purchase #7	$145.98	3.229%	$150.6937	$150.69	$150.70	$150.70
7 purchase totals =	$761.45		$824.8287	$824.83	$824.85	$824.70